A 

,-'-'" 










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THE 



CAR WHEEL 



GIVING THE RESULTS OF A 
SERIES OF INVESTIGATIONS 



BY 

GEO. L. FOWLER, M. E. 



W 



PUBLISHED BY THE SCHOEN 
STEEL WHEEL COMPANY 
PITTSBURGH, PA., 1907 



i LIBRARY of O0N«3iri£SS| 
Two Copies Racsivsij 

DEC 21 1907 

Oopyrieiit tntrj* 

lOLASS'* XXcWo,! 

COPY B. 



Copyright, 1907, by 
The Schoen Steel Wheel Company 



Tbc Fleming Press, New York 
10726 



(\ 






'/^JT,,^::^^^^ 



FOREWORD 

The solid forged and rolled steel wheel, referred 
to in the following pages of this book, was devel- 
oped and first manufactured by Mr. Charles T. 
Schoen, the pioneer builder of high capacity steel 
freight cars, and former president of the Pressed 
Steel Car Co. 

In the exploitation of large capacity cars Mr. 
Schoen was confronted with the problem of getting 
wheels to meet the requirements. The cast iron 
wheels put under these ioo,ooo-lbs. capacity cars 
failed repeatedly and the situation became serious. 
For instance, one railroad, which had in service 
several thousand of these cars, at one time con- 
sidered the expedient of marking all of them down 
to 8o,ooo-lbs. capacity in order to reduce the load 
on the wheels. 

The majority of wheel failures occur on moun- 
tain roads with steep grades and sharp curves where 
long and heavy brake applications are necessary, and 
the wheel flanges are subjected to severe shocks. 

Steel-tired wheels had given satisfactory service 
under passenger cars running over these mountain 
roads; but they were out of the question for freight 
equipment because of their prohibitive cost. The 
economical value of the high capacity car to the 
railroads having been demonstrated, the problem 
was to produce a wheel equal to or better than the 
steel-tired wheel in strength and at a cost for mileage 
less than that of the cast iron wheel. 

Mr. Schoen began his experiments in 1898, and 
early in 1901 the first machinery for making these 



wheels was designed. The Schoen Steel Wheel Co. 
was organized on May ii, 1903, and the business 
of making solid forged and rolled steel wheels 
established for the first time on a commercial basis. 

The enterprise has been a success from the 
start, fully justifying the large expenditure of money 
required in development work, and for the installa- 
tion of the necessary machinery. At the present 
time the company has a plant in operation, located 
at Pittsburgh, Pa., capable of producing 250,000 
wheels a year, and in connection with it open hearth 
furnaces with an annual capacity of 100,000 tons of 
steel for making the blooms from which the wheels 
are forged and rolled. The entire process from raw 
material to finished wheels is under the direct con- 
trol and supervision of the company. 

The Schoen solid forged and rolled steel wheel 
has proven such a pronounced success in America 
that it has attracted the favorable consideration of 
foreign railways. To supply this European and 
Colonial demand, The Schoen Steel Wheel Co., 
Limited, of Great Britain, was organized. The 
works are situated in Leeds, Yorkshire, and have 
an annual capacity of 100,000 wheels. 



Schoen Steel Wheel Co. 



Pittsburgh, Pa. 
November, 1907 



PREFACE 

When this investigation of wheels and tires was 
first undertaken its ultimate scope had not been 
decided upon, and it was the expectation that it 
would end when the first few comparative results had 
been obtained. It was made solely for the purpose 
of securing information regarding the standards of 
quality of metal and workmanship that must be met 
in the development of a new industry, the success 
of which depended on the production of a wheel 
that would at least meet the present requirements of 
railroad traffic. There was no intention of publish- 
ing the results, and this accounts for the apparently 
unfinished condition of much of the work. As 
soon as sufficient data had been obtained in one 
line of investigation to serve as a working basis, 
attention was turned to another branch of the sub- 
ject. Results obtained in the various tests referred 
to, therefore, must not be accepted as complete, but 
the records of the work so far done are made public 
with the thought that if they serve no other pur- 
pose the attention of railroad officers will be attracted 
to the field of railroad dynamics, as yet unexplored. 

In the presentation of the results obtained no 
attempt has been made to harmonize them with pre- 
vious theoretical deductions, nor has any attempt 
been made to build a theory upon them as a basis. 
Only elementary mathematical calculations have been 
introduced in order to show about what can probably 
be expected from a continuance of investigations 
along the same lines. 

Such a piece of work as this could not, of 



necessity, be carried on without material assistance 
from the railroads, wherever track and rolling stock 
was required, or defective and worn-out material was 
to be obtained. Such assistance has been generously 
and cheerfully given whenever it has been asked for. 
Acknowledgments are due to Messrs. A. W. Gibbs, 
D. F. Crawford, Wm. Mcintosh, G. W. Wildin, 
J. F. Deems, and Prof. Wm. Campbell, for materials 
furnished for examination and for assistance, and to 
Messrs. E. G. Ericson of the Pennsylvania Lines 
West, J. E. Childs, E. Canfield and G. W. West 
of the New York, Ontario & Western, and J. F. 
Deems of the New York Central, for the use of 
track and rolling stock. 



Geo. L. Fowler. 



New York 
November, 1907 



D 



ESIGN OF THE SOLID FORGED 
AND ROLLED STEEL CAR 
WHEEL. 



With a wheel made of one solid piece 
of steel having the requisite physical properties, it 
follows that a design can be used differing radically 
from a wheel having the center and the tire separate. 
The tire of a steel-tired wheel must be of such a thick- 
ness that it will admit of a reasonable amount of wear 
and at the same time leave enough metal in that 
part of the tire which is scrapped to insure strength 
against breakage during the last days of the life of 
the wheel. With the solid forged and rolled steel 
wheel, having the rim integral with and stiffened 
by the web, more wear can be safely allowed than 
where the stretching or breakage of the tire under 
the rolling and pounding action of service must be 
provided against. The solid forged and rolled steel 
wheel resembles somewhat the cast iron wheel in 
section, the difference being in the web, where there 
is a single plate instead of double plates and no 
brackets as in the standard cast iron wheel. 

The details of the dimensions of car wheels vary 
with the requirements of the railroads using them. 
There is a wide difference of opinion as to the best 
proportions for the thickness of the rim, while the 
dish and length of hub are determined to a great 
extent by the details of truck construction. This is 
especially so in electric railway work, where the wheel 
must be made to fit in between the motor on the 
inside and the journal boxes on the outside. Ordi- 
narily the dish of the wheel is determined by the 




SOLID FORGED AND ROLLED STEEL WHEEL FOR ENGINE TRUCK. 




SOLID FORGED AND ROLLED STEEL WHEEL FOR ENGINE TRUCK. 



-36"d/A 




SOLID FORGED AND ROLLED STEEL WHEEL FOR PENNSYLVANIA R.R. 




SOLID FORGED AND ROLLED STEEL WHEEL FOR AMERICAN CAR AND 
FOUNDRY CO. 




SOLID FORGED AND ROLLED STEEL WHEEL FOR TRAILER TRUCK 
INTERBOROUGH RAPID TRANSIT CO. 



Bj' ^ 




33 DM. 
SOLID FORGED AND ROLLED STEEL WHEEL FOR ELECTRIC STREET CARS. 




SOLID FORGED AND ROLLED STEEL WHEEL FOR ELECTRIC STREET CARS. 




SOLID FORGED AND ROLLED STEEL WHEEL FOR CLEVELAND AND SOUTH- 
WESTERN TRACTION CO. 




FORGED AND ROLLED STEEL WHEEL FOR PHILADELPHIA RAPID 
TRANSIT R.R. 



size of the journal box and its location relatively to 
the tread; but the form given to the web dishing, 
the thickness of the rim and the size of and shape of 
the flange and tread are matters for individual con- 
sideration in each case. 

In v^heels intended for steam railroad service the 
treads and flanges are uniform, corresponding to 
the M. C. B. standard. The variations in design 
are found in the webs and hubs, the thickness of 
rims, and occasionally a variation in the height of the 
flanges is allowed if the wheels are intended for 
engine trucks. 

Examples of these variations are shown in the 
accompanying diagrams. Thus, of two engine 
truck wheels illustrated one has a dished web, by 
which some yield is secured to compensate for the 
variations in the diameter of the rim due to tempera- 
ture changes, while on the other hand the wheel 
with a straight web is preferred by some motive 
power departments for exactly the same service. 

The wheel for the Pennsylvania Railroad has a 
rim 2 inches thick at the outer face of the tread, and 
the web is straight in section from the bend at the 
hub to the bend under the rim. The wheel for the 
American Car& Foundry Co. is thicker in the rim, 
and the web has a curved contour designed to com- 
pensate for expansion and contraction of the rim. 
Again, in the wheel designed for the Interborough 
Rapid Transit Co. the thickness of the rim has been 
increased to 3 inches although the diameter is but 31 
inches. This wheel also has the curved contour web. 

In electric service will be found the widest variations 
of practice. Street railways keep the floor of the 



13 



car as close to the rails as possible, so as to facilitate 
the entrance and exit of passengers. At the same 
time it is necessary to maintain a minimum diame- 
ter of wheel in order to provide sufficient clearance 
between the street pavement and the lowest point 
of the motors. The thickness of the rim is therefore 
determined by adding to the minimum allowable 
radius of the wheel a sufficient thickness of metal to 
raise the car to the maximum height deemed advis- 
able, and this dimension represents the amount of 
metal to be worn away. 

The wheel designed for the interurban cars of the 
Cleveland & Southwestern Traction Co. is an 
interesting example of a compromise between the 
M. C. B. standard wheel for steam roads and the 
lighter wheel ordinarily used in street railway work. 
The cars are heavy and the speed is moderately 
high, necessitating a web and hub of considerable 
strength and a flange high enough to hold the car 
to the rails at the speeds attained in the open coun- 
try and yet low enough to permit the wheels to pass 
over the rails and special work in the city. 



14 



COMPARATIVE PHYSICAL AND 
CHEMICAL TESTS OF SOLID 
FORGED AND ROLLED STEEL 
WHEELS, STEEL TIRES AND 
CAST IRON WHEELS. 

All the tires and wheels referred to in this work 
were bought in the open market, chosen at random, 
and tested under identical conditions in comparison 
with each other. They represent the principal brands 
in use giving satisfactory service, and the results 
stand on the basis of each sample representing the 
average of its class and brand. They will be desig- 
nated as Tires A, B, C and D, Wheels E and F and 
Schoen Wheel. 

Tests were made of the tensile strength, including 
the limit of elasticity, per cent, of elongation, and the 
reduction of area at the point of fracture. The steels 
were tested for hardness by a drop of the Mattel scale. 
Abrasion tests were made in order to find the resist- 
ance of the several materials to grinding at various 
points below the tread. Specimens were also cut 
for the determination of the specific gravity of the 
metals at diff'erent points below the tread. Chemi- 
cal analyses were made from samples of each tire 
and wheel taken from a point below the center of 
the tread. Finally, a series of microphotographs 
were taken of etched specimens of the metals in 
order to show their structure and the relation of that 
structure to the physical and chemical properties 
previously determined independently. 

The chemical analyses for carbon were all made 
by the combustion process and the tensile tests were 



15 




LOCATION OF TENSILE TEST SPECIMENS. 

made in the usual manner, using test pieces 2 inches 
long between marks. The reason for choosing this 
length was that the curvature of the treads of the 
wheels and tires made it impossible to cut longer 
ones. These specimens were cut from the points C, 
D, and E, as indicated on the diagram showing 
the location of tensile test specimens. These test 
pieces were cut on a chord of the tire and gave an 
available length of 2 inches on the reduced area | 
inch in diameter, the center of which was carefully 
located at the point indicated on the drawing. The 
tensile tests were made in an Olsen testing machine 
of 100,000 lbs. capacity, and the results obtained are 
given in detail in the following table marked " Com- 
parative Tests of Steel Wheels and Tires." 

The averages of these are collected and pre- 
sented in a condensed form in the table marked 



16 



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Maximum 

Load per 

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Lbs. 


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Breaking Load 

per square inch 

of Section. 

Lbs. 


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Approximate 

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Elasticity per 

square inch of 

Section. 

Lbs. 


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Limit of 
Elasticity to 
Total Load. 


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17 



AVERAGE OF COMPARATIVE TESTS OF STEEL WHEELS 
AND TIRES. 





n 


|j, 


U 


s§ 


JJ 


"o 








3 

"2 ri 


9 fi 








u 


Tire or Wheel. 


O P) 


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IS 




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o o 


c c 
S.2 


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W 


CTire 


13-50 


15.89 


116,761 


"3.352 


77.133 


66.06 


818 


A " 


"•35 


11.45 


124,018 


121,951 


91,646 


73-89 


817 


D " 


20.90 


29.50 


115.963 


104,095 


95,008 


81.92 


783 


B '< 


15.40 


19-33 


114,519 


107,989 


95.232 


83.18 


799 


E Wheel 


7.40 


6.87 


113,610 


111,184 


82,388 


72.63 


872 


F 


14.90 


17-13 


114,477 


110,857 


95,580 


83-50 


875 


Schoen Wheel 


8.66 


12.32 


124,386 


121,523 


104,124 


86.45 


1125 



"Average of Comparative Tests of Steel Wheels 
and Tires/* 

From this table it will be seen that in the wheels and 
tires examined the average maximum tensile strength 
varied from 113,610 lbs. to 124,386 lbs. per sq. in. 
of section; that the elongation in 2 inches varied 
from 7.40 per cent, to 20.90 per cent.; the limit of 
elasticity from 66.06 per cent, to 86.45 P^^ cent, of 
the maximum tensile strength; and the hardness 
from 783 to 1 125 points on the Martel Scale. 

In reviewing these results it is necessary to con- 
sider the relative influence of the chemical composi- 
tion on them. This is given in the table marked 
"Chemical Composition of Steel Wheels and Tires." 

As would be expected the low carbon content of 
the D tire is accompanied by comparatively low 
tensile strength, high ductility and low hardness. 

At the same time it is evident that the work put 



CHEMICAL COMPOSITION OF STEEL WHEELS 
AND TIRES. 



Wheel. 



Carbon. 



Phos- 
phorus. 



Sulphur. 



Manga- 
nese. 



Silicon. 



C Tire . . . 

A " . . . 

D " . . . 

B '< . . . 

E Wheel . . 

F " . . 
Schoen Wheel 



0.616 
0.716 

0-573 
0.676 
0.646 
0.631 
0.690 



0.048 
0.095 
0.075 
0.061 
0.071 
0.081 



0.023 
0.038 

0-035 
0.029 
0.042 
0.000 



0.698 

0753 
0.763 

0-833 
0.978 
0.775 
0.870 



0.305 
0.263 
0.509 
0.254 
0.249 
0.241 
0.094 



on the wheel is an influential factor in all of these 
results and there is a variation of tensile strength 
and ductility that is not fully accounted for by the 
variation of carbon content. Take as an extreme 
example the E wheel and the Schoen wheel. There 
is a variation of but .044 per cent, in carbon, and 
yet the maximum tensile strength of this E wheel 
was but 113,610 lbs. per sq. in. while that of the 
Schoen wheel was 124,386 lbs. with a correspond- 
ing elongation in 2 inches of 7.40 per cent, and 
8.66 per cent, respectively, while the limit of elas- 
ticity was 72.63 per cent, and 86.45 P^^ cent, of the 
tensile strength respectively. The actual variation 
in limit of elasticity was much greater, because of the 
higher base of comparison with the Schoen wheel; 
the limit of elasticity of the E wheel being but 79.12 
per cent, of that of the Schoen wheel. In making 
these tensile tests great care was exercised not only 
in the preparation of the specimens, but in making the 
tests themselves. The machine was run slowly after 
a stress of 50,000 lbs. had been reached, so that the 
limit of elasticity could be very accurately determined. 



19 



COMPARATIVE RESULTS OF PHYSICAL TESTS OF 

SCHOEN STEEL WHEELS WITH OTHER 

WHEELS AND TIRES. 





^H 


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Tire or Wheel. 




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2 m ° 


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p^ 


1-, 

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Schoen Wheel . . . 


lOO.OO 


100.00 


100.00 


100.00 


100.00 


100.00 


100.00 


A Tire 


99.70 


131.06 


92.94 


100.35 


88.02 


85.47 


72.62 


C " 


9387 


155-89 


128.98 


93.28 


74.08 


76.41 


72.71 


D « 


9323 


241.34 


239-45 


85.66 


91.25 


94.76 


69.60 


B « • . . . . 


92.07 


177-84 


I 56.90 


88.86 


91.47 


96.22 


71.02 


F Wheel 


92.03 


172.05 


139.04 


91.22 


91.79 


96-59 


77.78 


E " 


91-34 


85-45 


55-76 


91.49 


79.12 


84.01 


77-51 



A comparison of the results obtained with all 
wheels and tires with those obtained with the Schoen 
steel wheel are given in the table marked "Com- 
parative Results of Physical Tests of Schoen Steel 
Wheels with Other Wheels and Tires" in which the 
results obtained with the Schoen wheel are taken 
as a base, and the results obtained with the other 
wheels and tires are given in percentages of that base. 
From this table it appears that the Schoen wheel 
leads all of the others in the items of tensile strength, 
limit of elasticity, per cent, of limit of elasticity to 
ultimate strength and in hardness. 

The tests for hardness were made with a drop 
arranged with a pyramidal punch. The principle 
on which this work was done was to measure the 
force of a blow delivered by the punch on the smooth 
face of the metal to be tested, as well as the amount 



of metal displaced by the blow. This method of 
testing was devised by Col. J. T. Rodman of the 
United States Army. It was afterwards developed 
and formulated by Lieut. Col. Mattel of the French 
army and was then adopted as a standard test by 
the French government. The results obtained are 
known as the degrees of hardness by the Mattel 
scale. By his investigations Col. Mattel showed 
that the amount of metal displaced by the punch 
varied inversely as the hardness and directly as the 
weight of the drop and the height of the fall. 

In this investigation the Rodman pyramidal punch 
was used. It was fastened to a drop weighing, to- 
gether with the punch, 2.2616 kilograms, and the 
height of fall was 600 millimeters. The punch was 
of hardened tool steel, carefully ground to form, and 
it withstood the work without deformation. 

The specimens for the test were cut from the tires 
and wheels at the same points as the tensile test 
pieces as indicated at C, D, and E, and the results 
obtained are given with the other physical properties 
in the several tables. 

These tests show the Schoen wheel to have been 
the hardest of the seven specimens tested, and that 
the D tire was the softest. This was to be expected 
judging from the carbon content; but we note that 
while the A tire has a higher percentage of carbon 
than the Schoen wheel, for some reason the latter is 
the harder of the two. 

For the abrasion tests a cylinder | inch in diameter 
was cut from a point near the center of the tread of 
each wheel, extending vertically down into the body 
of the metal. This was placed in a frame, with the 



end that was at the tread resting on an emery 
wheel. A load of 2 lbs. ii| oz. was put on the 
upper end of the cylinder to hold it down on the 
wheel. This weight was selected after some pre- 
liminary trials made to ascertain the pressure that 
could be used without heating the material or grind- 
ing it away too rapidly so as to make the count 
smaller than would be convenient for making com- 
parisons. To this weight must be added the weight 
of the cylinders themselves, which varied about 
0.54 oz., a variation which was duly considered and 
the proper allowance made therefor, although it is 
practically a negligible quantity. 

The wheel used was made by the Carborundum 
Co., and was 10/4 inches in diameter and | inch 
thick when new. At the conclusion of the tests the 
wheel was worn to a diameter of 10/^ inches. It was 
known on the maker's schedule as Grit 120; Grade 
H., Bond G 9. It was run at a speed of about 
2,500 revolutions per minute. 

While grinding, a constant and uniform stream of 
water was kept running on the wheel and specimen, 
and at the conclusion of the test the specimens were in- 
variably cool and showed no signs of heating whatever. 

The counting of the revolutions was done by means 
of a special counter coupled to the shaft and having a 
worm meshing with a gear of 25 teeth mounted on a 
shaft to which a revolution counter was attached. The 
reading of the counter was, therefore, multiplied by 
25 to obtain the number of revolutions of the wheel. 

In addition to the regular tests, a cylinder was 
cut from the same position in a chilled cast iron 
wheel, and the results of its abrasion test, as well as 



















































... 
















































































































































































































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/f4 



DIAGRAM OF ABRASION TESTS OF STEEL TIRES AND WHEELS, SHOWING 

RELATION OF RATIO OF WEAR AT VARIOUS DEPTHS BELOW TREAD 

TO REVOLUTIONS OF EMERY WHEEL. 



»3 



those of the wheels and tires, have been plotted and 
shown in the illustration, ''Diagram of Abrasion Tests 
of Steel Tires and Wheels." The abscissas indicate the 
location of the metal below the tread, and the ordinates 
the number of revolutions of the wheel required to 
grind off | inch from a cylinder J inch in diameter. 
It will be noted that in every test there is a rise 
in the number of revolutions at a point about | 
inch below the surface of the tread, or for the space 
between ^ inch and | inch. Had the work been 
done in rotation this peculiarity might have been 
attributed to a change in the texture of the wheel, 
glazing, heating the material, or a similar cause. 
The tests were started, however, before all of the 
cylinders had been finished, and those from the A, 
B, C and D tires were well along when a start was 
made with the cylinder cut from the Schoen wheel. 
This was worked down in rotation with those from 
the tires, when that from the E wheel was intro- 
duced, and this was followed in the same way by that 
of the F wheel, so that the wheel structure itself is 
responsible for the diagram. By reducing these 
diagrams to an average the results are as follows: 



AVERAGE ABRASION PER }/» IN. OF TIRES AND WHEELS. 



Tire or Wheel. 


Revolutions. 


Linear Feet. 


Schoen Wheel . . . 


32.63s 


86,483 


E Wheel 


30,660 


81,249 


C Tire 


28,205 


74,743 


B " 


26,320 


69,748 


F Wheel 


25,540 


67,681 


A Tire 


23,270 


61,666 


D " 


21,445 


56,729 


Cast Iron Wheel . . 


S.485 


14.535 



Z4 



Reducing these to percentages on the basis of the 
Schoen Wheel we have: 



Tire or Wheel 



Per Cent. 



Schoen Wheel 

E Wheel . . . , 

C Tire . . . . 

B » . . . . 

E Wheel . . . . 

A Tire . . . . 

D " . . . . 

Cast Iron Wheel 



93-95 
86.42 
80.65 
78.26 
71.30 
65.71 
16.81 



From this it appears that the resistance of the 
Schoen wheel to abrasion was greater than that of 
any of the other wheels and tires with which it was 
compared. The cast iron wheel gave the lowest 
resistance of any cylinder tested. The wheel was of 
good material, with a depth of chill of about f inch. 

An explanation of the peculiar rise in the number 
of revolutions required to grind these tires between 
J inch and | inch will be brought out in the dis- 
cussion of the microphotographs. The examination 
made of the specific gravities of the metal of the 
tires and wheels at different points below the surface 
of the tread also tends to show a reason for the 
peculiar rise in the rate of abrasion by the emery 
wheel. From this examination it appears that with 
slight local aberrations the density of the material 
increases from the tread down to a depth of about 
I inch and then decreases down to 2 inches. A few 
observations made below these depths show that 
there is again a tendency to increase in density as 
the inner edge of the tire is approached. There was, 



^5 



however, a variation of this condition found in the 
rim of the Schoen wheel. Although there was 
a tendency to follow the general behavior of the 
other specimens it was along a wavy line corre- 
sponding, but not in exact location, with the variation 
in the texture of the grain which will be brought out 
in the microphotographs to be discussed later. 

Another peculiarity that was developed is the 
relation of hardness, resistance to abrasion and ten- 
sile strength to the specific gravity of the material. 

It will be noted that the rate of wear of the cast 
iron wheel, as shown on the diagram, was much 
greater than that of any of the steel tires or wheels. 
The rapid fall in the number of revolutions per | 
inch of metal removed as the chill was worn away is 
easily accounted for, but it was not expected that the 
variations from the results obtained with the steel tires 
would be so great as they were. In the laboratory 
the metal and wheel were kept cool, so that at no 
time did the temperature rise, even on the face of 
the specimen, above that of the hand. As these 
abrasive tests have been checked in other ways, as 
will be shown later, it appears that the avoidance 
of heat is the explanation of the great difference. 

It must be borne in mind that the primary object 
of these investigations was to ascertain to what extent 
the metal entering into the construction of the Schoen 
wheel fulfilled the requirements of actual service 
as determined by comparison with other wheels 
already upon the market and doing satisfactory work. 

The conclusions to be drawn from a general re- 
view of the results obtained in this investigation are 
as follows : 



26 



From the physical tests of the metal of the Schoen 
solid forged and rolled steel wheel, it appears that 
it is the strongest of any of the tires and wheels 
examined. This strength appears in the maximum 
stress to which the metal was subjected, the point at 
which rupture took place and the limit of elasticity, 
all of which were higher than in any other wheel or 
tire, with the single exception of that of the A tire. 
This tire had a breaking load exceeding that of the 
Schoen wheel by but 428 lbs. per sq. inch of section, 
an amount that is unimportant. 

The limit of elasticity, as expressed both in actual 
figures and in the percentage of the total load, was 
far higher in the Schoen wheel than in any of the 
others. 

The ductility of the metal of the Schoen wheel, 
as indicated by the elongation of the tensile test 
pieces, is less than that of any of the other speci- 
mens with the exception of the E wheel. Here 
there is a difference of nearly 15 per cent, in favor 
of the Schoen wheel, despite the fact that the E 
wheel contains nearly .05 per cent, less carbon. 
This is probably due to the difference in the amount 
of work put on the two wheels. 

In hardness the Schoen wheel stands the highest 
on the scale. This is shown in another way by the 
abrasion tests, which show the Schoen wheel to be 
the slowest of any to grind away. 

In specific gravity the Schoen wheel is the highest. 

The chemical composition is of course a matter 
that is regulated by specifications and a review of 
these since the introduction of steel-tired wheels 
has shown a steady advance in the carbon content. 



Z7 



The makers of the Schoen wheel have placed 
their wheel next to the highest in carbon con- 
tent. This explains, in part, the high ultimate 
tensile strength, although it cannot account for 
it altogether because the Schoen wheel ^eads the A 
tire, which has a higher carbon content, in elasticity 
and maximum load, and in ductility is above the E 
wheel having a lower carbon content. In this analysis 
special attention is directed to the sulphur, not a 
trace of which could be found in the Schoen wheel 
specimens under examination. 



28 



M 



ICROGRAPHIC RECORDS SHOW- 
ING THE PENETRATION OF 
WORK AND CHARACTER OF 
HEAT TREATMENT. 



The physical properties of the steel in these wheels 
and tires having been determined, an examination 
with the microscope was made of samples from 
each. In the preparation of the specimens for this 
work strips were cut from each wheel and tire in 
accordance with the lines shown on the diagram. 
The numbers 1,2,3 ^^^ 4 ^^^ ^^^ ^^^ identification 
of the strips and are used in connection with 
the photographs, all of which were made with a 
magnification of 88 diameters. 




SECTION OF TIRE SHOWING LINES OF LOCATION OF MICROPHOTOGRAPHS 



29 



Referring first to the microphotographs of the D 
tire, Nos. i to 6, Nos. i to 5 were taken in strip 
No. 4, at the tread and at | inch, | inch, and i inch 
below the tread respectively, and No. 6 at i inch 
below the tread in strip No. 3. These photographs 
show an exceedingly fine granular structure, indi- 
cating careful heat treatment, a low average per- 
centage of carbon and an abundance of ferrite. The 
structure becomes somewhat coarser as the metal is 
penetrated and the normal structure is reached at 
a depth of about i in. It will also be seen that 
there is a slight difference between the structures of 
the metal as illustrated by the two photographs Nos. 
5 and 6 which were taken at a depth of i in. below 
the tread in strips 4 and 3 respectively. No. 5 is 
the finer, showing that the metal received more 
work at that point than it did deeper in on 
strip No. 3. This D tire had the finest grain 
and the most uniform structure of the samples 
examined. On the other hand, the photographs 
corroborate the chemical analysis of low carbon 
content, possibly down to 0.50 per cent., as indi- 
cated by the proportion of ferrite (white) and 
pearlite (black). 

Next in order of fineness of grain comes the C, B 
and A tires respectively. Here again the relative 
amounts of ferrite and pearlite give an approximate 
indication of the amount of contained carbon, from 
which it would appear that the B and C tires would 
not run over 0.60 to 0.65 per cent, while the A may 
rise to 0.70 per cent. 

The material of the B tire shows a practically 
uniform texture of grain throughout its whole depth, 



30 




No. I. At Edge of Tread. 



No. 2. 's In. Below Tread. 




No. 5 I In. Bf.low Treau. No. 6. i In. Below Tread. 

MICROPHOTOGRAPHS OF TIRE D. 88 DIAMETERS. 



31 




No. 9. lA Im. Below Tread. No. 10. i In. Below Tread. 

MICROPHOTOGRAPHS OF TIRE C. 88 DIAMETERS. 



33 



with no decarbonization at the tread due to heat 
treatment, although this is undoubtedly due to the 
tire having been turned before being examined. 

In the C tire, which was new, it will be seen that 
the outer layer of the material next to the tread, as 
indicated by the photograph No. 7, was decarbonized 
by the action of the heat treatment to which it was 
subjected. The presence of ferrite is very marked 
all the way across the tread, but below the surface, 
as indicated by the photographs Nos. 8, 9 and 10, 
which were taken at depths of | in., | in., and i in. 
below the tread respectively, the grain assumes the 
normal condition for the steel at its finishing tem- 
perature, although it is somewhat finer at the edge 
strips Nos. I and 4 than in the center strips Nos. 
2 and 3, indicating failure of the work to penetrate 
the center. 

The A tire has such a high carbon content that 
the absence of excess ferrite causes the grain to become 
obscure; it was possible to bring the formation out in 
part only by oblique illumination. When viewed 
under the microscope with the light adjusted to 
the best advantage a decided coarsening of the grain 
is noted at successive points below the tread. For 
example, at the surface the grains are apparently about 
the same size as those immediately below the decar- 
bonized shell of the tread in the C tire, but the grain 
coarsens rapidly, and at a depth of i in. it is some- 
what coarser than that of the C tire. The structure is 
interpreted from the microphotographs in the accom- 
panying diagram made at the same magnification. 

The E wheel has an exceedingly coarse structure with 
traces throughout of inequality of carbon content 



35 



and disappearance of the grain. This is especially 
noticeable in photographs Nos. 19 and 20 and ap- 
pears in the others to a greater or less extent, showing 
an unevenness of structure that is suggestive of cast 
steel. This is discussed elsewhere in connection 
with a shelled-out wheel of the same make. The 
penetration of work was apparently very slight as is 
shown by the large size of the grains in No. 17, taken 
at the surface of the tread, and the increasing size of 
structure as shown in Nos. 18, 19 and 20 taken at 
depths of 1^ in., | in., and i in. respectively. 

The F wheel has a coarser grain than the A, B or 
C tire and is slightly coarser than that of the D tire. 
The carbon content appears to be about the same 
as that of the C tire, or somewhat above 0.60, and 
this is checked by the chemical analysis. The sur- 
face decarbonization which is so marked in the case 
of the C tire appears in this one also, as indicated 
by the increase of the amount of ferrite accom- 
panied by softening of the surface. The large size 
of the grain in this wheel, as illustrated by photo- 
graphs Nos. 21 to 26, is caused by the heat treat- 
ment to which this wheel was subjected. There has 
evidently been no work put upon it after the final 
heating. This also explains why there is compara- 
tively little enlargement of the grain going down 
from the surface of the tread. The photograph No, 
21 was taken at the surface of the tread and the others 
followed at depths of | in., | in., i in., 2| in., and 
2| in. respectively. 

The B tire is typical of the others and needs only 
a word of explanation of the microphotographs Nos. 
27 to 30, which were taken at the surface of the 



36 




No. 15. 



In. Below Tread. No. 16. i In. Below Tread. 

MICROPHOTOGRAPHS OF TIRE A. 88 DIAMETERS. 



37 




p3//V, 



/ /A/, 



INTERPRETATION OF GRAIN STRUCTURE IN TIRE A AT VARYING DISTANCES 
BELOW SURFACE OF TREAD. 



39 



tread and at depths of | in., ^ in., and | in. re- 
spectively. From these the gradually increasing size 
of the grain is apparent, though from its large di- 
mensions, even at the tread, it would appear that this 
particular tire was finished at a high temperature. 

The microphotographs of the Schoen wheel show 
that for the first | in. of depth it has the finest 
structure of any of the wheels and tires examined, 
but below this depth its grain increases in size in a 
comparatively uniform manner, though with a varia- 
tion to be noted later. The steel contains but a trace 
of ferrite, indicating that the carbon content is about 
the same as that in the A tire. Here again, owing 
to the absence of sufficient ferrite to outline the grain 
clearly, it was necessary to photograph by oblique 
illumination, and it was under this light that the ac- 
companying sketches to show the grain's size were 
made. The microphotographs closely check the 
abrasion tests and the determinations of specific 
gravity. 

There are two well-defined zones in the rim of 
the Schoen wheel that are evidently due to the 
rolling. One is at a depth of | in. and the other 
f in. below the surface of the tread. This is best 
illustrated by the accompanying diagram of the 
microstructure in the Schoen wheel, in which the 
four strips and the location of the microphotographs 
are roughly indicated. 

Strip No. I shows a very fine grain at the surface 
with carbon well below 0.50 per cent. This structure 
runs down for about -^ in., where there begins a 
gradual increase of the grain size until the normal 
dimensions are reached at about yV in. below the top 



40 




No. 19. % In. Below Tread. No. 20. i In. Below Tread. 

MICROPHOTOGRAPHS OF WHEEL E. 88 DIAMETERS. 



41 



of the flange. The first 2V iri- is formed of a very 
fine mixture of about equal proportions of ferrite 
and pearlite, and below this the ferrite gradually dis- 
appears and the grains increase in size. At a depth 
of -Y2 in. the ferrite appears as a discontinuous band 
or envelope around the grains of pearlite, indicating 
that the carbon content is about 0.70 per cent. This 
increase in the size of the grains continues dow^n- 
ward until they reach their maximum at a depth of 
about I in. 

In strip No. 2 there is the same fine-grained sur- 
face structure {a) corresponding to that of No. i. 
The depth of this decreases from one side of the 
strip to the other and is about ^ in. thick at the 
corner. This structure is shown in the photograph 
No. 31. On the right hand side two zones will be 
seen, one of which, starting at /i, is of very fine 
pearlite. The point of maximum coarseness is at ^i. 
This is not really a coarse grain in itself, for it is 
fine even when compared with that of the D tire. 
Below ci there is an abrupt change to extreme fine- 
ness again at /2. This is followed by a gradual 
increase in the size of the grain down to c2, 
where the normal structure is found at a depth of 
about I in. 

In strip No. 3 there is the same fine grain at the 
surface, as shown in the photograph No. 32, which 
extends down to a depth of about 5V in. The ex- 
treme outside shows almost entire absence of car- 
bon, or nearly pure ferrite. This is followed by a 
gradual increase in the amount of carbon until, at 
a depth of about ^V in., a fine grain structure almost 
wholly of pearlite is indicated at /i. Next comes a 



43 



uniform increase in the size of the grains until they 
reach their maximum at the point marked ci, where 
there is an abrupt change to a structure of great 
fineness which in turn increases in size to a maxi- 
mum at c2, when there is a second abrupt change 
to extreme fineness at f^. Below this there is a 
gradual increase in the grain size until the normal 
structure is reached at about i in. 

In strip No. 4 there is the same decarbonized outer 
layer (a) which is about ^ in. thick at the center, 
thickening towards the right in the direction of the 
edge of the wheel rim. This structure differs in 
appearance from the corresponding area in No. 3, 
due to the distortion of the grain by mechanical 
treatment of the metal after ferrite or pure iron 
became excessive as the result of burning out the 
carbon on the surface of the steel. The size of the 
grain increases from fine at /i, to a maximum coarse- 
ness at ci, I in. below the surface where there is 
the same abrupt change as before to a fine structure 
at /2. This will be seen by a reference to photograph 
No. 38. The grain again increases to a maximum 
coarseness at c2, with another change to extreme 
fineness at /3, at a depth of about | in. Beyond 
this point the grain increases uniformly until the 
normal size is reached at a depth of i in., as indi- 
cated by photograph No. 36, and the diagram of 
grain sizes. 

These changes in grain size are accounted for by 
the successive heat and mechanical treatments to 
which the Schoen wheel was subjected. 

The conclusions drawn from this work with the 
microscope are practically the same as those reached 



44 




No. 25. ty^ In. Below Tread. No. 26. 2% In. Below Tread. 

MICROPHOTOGRAPHS OF WHEEL F. 88 DIAMETERS. 



45 



by a study of the physical and chemical tests. It is 
apparent that the Schoen wheel is quite equal to 
the best tires, as regards depth of finish and the 
fineness of the grain in the steel. 



N?l. 










N?2. 



N2 3. 




N54. 



1150 /> Ao /; 



-.-y—^ 









DIAGRAM ILLUSTRATING GRAIN STRUCTURE OF SCHOEN STEEL WHEEL. 



47 




INTERPRETATION OF GRAIN STRUCTURE IN SCHOEN WHEEL AT VARYING 
DISTANCES BELOW SURFACE OF TREAD. 



48 



\ 


^^vV -■ 






'-(:m 


■ 7V, ■■■:■■:• 












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'< ■ 






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^- ;'>'/.: ':- rv". 


' ■■ >'". ' 1 



No. 27. At Edge of Tread. 





No. 29. i^ In. Below Tread. No. 30. 14 In. Below Tread. 

MICROPHOTOGRAPHS OF TIRE B. 88 DIAMETERS. 



49 




No. ji. At Edge of Tread. 



No JI. At Edge of Tread. 




No. 3j. Ys In. Below Tread. No, 54. ^ In, Below Tread. 

MICROPHOTOGRAPHS OF SCHOEN STEEL WHEEL, 88 DIAMETERS, 



51 




No. 37. At Outer Edge of Tread. No. 38. ^ In. Below Outer Edge of Tread. 

MICROPHOTOGRAPHS OF SCHOEN STEEL WHEEL. 88 DIAMETERS 



53 



T 



HE SHELLED-OUT WHEEL. 
A POSSIBLE EXPLANATION OF 
THE CAUSES OF WHEEL AND 
TIRE FAILURES. 



The service that can be expected from any wheel 
depends on the soundness and homogeneity of the 
metal of which it is composed. Irregularity of tex- 
ture must necessarily result in irregular wear, while 
local defects are apt to result in an immediate failure. 
Of such failures one that is the cause of much an- 
noyance and trouble is that known as shelling out. 
It was for the purpose of ascertaining, if possible, 
the causes of this shelling out of wheels and tires 
that an examination with the microscope of a num- 
ber of defective tires that had failed in service was 
undertaken. 

The Rules of Interchange of the Master Car Build- 
ers' Association define a shelled-out wheel as one 
"with a defective tread on account of pieces shelling 
out." This is a poor definition; it may be supple- 
mented by saying that the common understanding 
of a shelled-out wheel is one in which pieces from 
the tread have flaked oflF, due to inherent defects in 
the metal, such as the laminations so frequently 
found in wrought iron boiler-plates. It will be 
seen later that the analogy in the case of steel wheels 
is very close. The cause of shelling out of cast 
iron wheels is outside of this investigation and will 
not be considered. 

The samples of defective material investigated 
include one of each brand of wheel and tire pre- 
viously referred to in these pages, and were obtained 



55 



from several railroad companies. Each of these 
wheels and tires had one or more shelled-out spots 
on the tread, and there were also places on each 
where no signs of shelling out could be detected. 
The general appearance of two samples is shown in 
the accompanying photographs, and these may be 
considered as characteristic of all. 

A section was taken at the spot where the worst 
shelling was found and another through a place on 
the tread where the metal showed no external signs 
of deterioration. These sections were then cut into 
strips whose centers lay along the lines i, 2, 3, and 
4 respectively. (See page 29.) The strips were then 
polished, etched and photographed. The photo- 
graphs were taken at the tread, and at intervals 
approximately | in., ^ in., | in., and | in. below. 
This was not strictly followed in all cases, since the 
examination was governed, to a certain extent, by the 
structure of the material examined, as it appeared 
under the microscope. 

Nos. 39 to 42 show the structure of the C tire at 
the point where the worst shelling out occurred. In 
strip No. I, which ran down into the wheel from the 
flange, the metal shows a fairly good fine-grained 
structure at the edge and well down into the rim. 
In No. 39, which was taken at ^ in. below the edge, 
spots of manganese sulphide are visible. The metal 
shows a good structure in all of the strips down to 
I in. in depth, wherever the photographs avoid the 
serious defects. In No. 40, however, which was 
taken from strip No. 3, there is a distinct flaw due 
to the presence of slag. The same kind of flaw 
appears, very pronounced, in the photographs Nos. 



56 



41 and 42, which were taken from strips Nos. 2 and 3 
respectively, and through which a continuous line 
of slag extends. At other points adjacent to these 
defective places normal conditions and structure of 
metal were found. 

Photographs Nos. 43 and 44 were taken from 
points on strip No. 3, at depths of J in. and J in., 
cut from an apparently solid piece of metal, and yet 
they show the presence of pronounced slag flaws. 
These flaws had not developed into shelled-out spots, 
but it is reasonable to suppose that it was only a 
matter of time when they would have done so. 

Comparing this defective C tire with the sound 
new tire, the absence of a decarbonized surface on 
the defective tire is to be noticed, while it was very 
apparent in the new tire and can be clearly seen in 
photograph No. 7 (page ^^). This is accounted for 
by the fact that the defective tire was in service and 
this soft outer shell had been worn away. 

The balance of the material of the defective C 
tire is normal in structure, except that the manganese 
sulphide globules are large. Its failure is readily 
accounted for by the slag flaws found scattered 
through the whole body of the material as shown in 
Nos. 40 to 44. 

The B tire failed from the same cause as the C 
tire. The structure of the metal is normal through 
a large part of the sections, but contains occasional 
slag cracks, and the characteristic markings of manga- 
nese sulphide, as shown in No. 45. In the other 
parts of the tire precisely the same conditions exist as 
in the C tire, namely, slag cracks, as shown in Nos. 
46, 47, and 48, which were taken at various depths. 



57 



and where no indication of shelling out had appeared 
at the time that the tire was removed from service. 
The presence of such large slag veins as those shown 
in Nos. 46 and 47 leaves no room for doubt as to 
the cause of failure. The presence of manganese 
sulphide was also indicated in the new B tire, but 
no slag veins are revealed. 

Nos. 49 and 50 were taken from the defective A 
tire. If the metal of this tire is compared with that 
of the sound new tire, it will be seen that there is no 
variation in the normal structure of the material to 
indicate a difference in the wearing quality, so that 
the failure of the shelled-out tire is undoubtedly due 
to the slag flaws clearly shown in the photographs. 

In the shelled-out D tire normal structure was 
found but interspersed with slag cracks as in the 
other defective tires. These are shown in Nos. 51 
to 54, some of which were taken close to the edge 
of the tread. In some places there were spots of 
manganese sulphide near the edges, but the cause 
for failure is the presence of the slag flaws that form 
planes of extreme weakness. In photograph No. 51 
such a flaw is shown, which eventually must have 
caused shelling out. Another example of the same 
sort is shown in No. 51. 

In the E wheel the slag flaws can be seen in Nos. 
55 and 56, which were taken from the shelled-out 
portion. In No. 55 there is a distortion of the 
slag defects due to the forging, and in No. 57 there 
can be seen a slag crack which existed in the metal 
with no visible defect on the surface. 

The material in this particular wheel is bad in every 
particular. The carbon content is low, apparently 



58 



ranging from 0.35 to 0.40 per cent. The effect of 
both the work and heat treatment is practically nil and 
the structure looks like that of untreated cast steel or 
a metal that has been overheated. The surface shows 
the effect of cold rolling in the mixture of ferrite and 
slag, the whole having a schistose appearance. The 
presence of so much slag, as shown in Nos. 55, 56 
and 57, renders the wheel totally unfit for service. 
The grain is coarse, as is seen in photos Nos. 58 and 
59, and resembles that in the new wheel of the same 
brand that was examined. The carbon content of 
the new wheel, however, was apparently much 
higher. 

In the shelled-out portion of the F wheel the slag 
flaws also appear well down in the metal. (See Nos. 61 
and 62.) What was said of the defective E wheel 
applies to the F wheel. The carbon content seems 
to be low, while the presence of large quantities 
of slag, photograph No. 62, caused the many lines 
of weakness along which rupture occurred. 

At the time this examination was being made three 
specimens of the Schoen solid forged and rolled steel 
wheel were obtained, two from shelled-out wheels and 
one from a section of a wheel that had been purposely 
burned in heating during manufacture. An examina- 
tion of the photographs of the two defective wheels, 
Nos. 67 to 70, shows that there are defects in the interior 
of the metal that were undoubtedly the cause of the 
shelling out, but there is no evidence of slag. The 
same characteristics are to be noted in Nos. 65 and 
66 of the specimen that had been purposely burned. 
The three specimens are examples of burned steel 
in which there is no evidence of slag. 



59 



From these photographs it is evident that the 
cause of the failure of all of the wheels and tires, 
except the Schoen wheels, was due to the pres- 
ence of slag flaws occurring near the surface of 
the tread. 

It appears, therefore, that there are at least two 
causes for the shelling out of steel tires and wheels, 
namely, slag flaws and overheating. 



60 





SHELLED-OUT STEEL TIRE AND WHEELS 



6i 




No. 39. At i^ In. Beijiw Siii iiin Si'cir. 




No. 40. At Edge of Shelled Spdt. 




N(l 41 SlloWlNf. Sl\( (.1 WK 



No. 42. S[i(iui\(, Si ,\(. CKACKi 




No. 43. 5^ In. Below Tread of Solid No. 44. J^ In. Below Tread 01 Solid 

Metal. Metal. 

MICROPHOTOGRAPHS OF SHELLED-OUT TIRE C. 50 DIAMETERS. 



63 




No. 45. At J^ In. Below Shelled-out 
Spot. 



No. 46. Slag Crack in Solid Section 
OF Tire. 




I ^1 



No. 47. Slag Crack in Solid Part of No. 48. Manganese Bisulphide Spots. 

Tire. 
MICROPHOTOGRAPHS OF SHELLED-OUT TIRE B. 




No. yo. Slag Flaw Near Edge of Solid 
Metal. 
MICROPHOTOGRAPHS OF SHELLED-OUT TIRE A. 



65 




No. 53. Slag Crack Near Edge in No. 54. Slag % In. BiiLuw 1 kiiad in 

Solid Metal. Solid Metal. 

MICROPHOTOGRAPHS OF SHELLED-OUT TIRE D. 50 DIAMETERS. 



67 




No. 59. Structure at Edge of Tread. No. 60. Slag at Center of Tread. 

MICROPHOTOGRAPHS OF SHELLED-OUT WHEEL E. 50 DIAMETERS. 



69 




No. 6i. Slag ^s In. Bei o\v Shei lkd-out 
SroT 



No. 62. Slag ^ In. Below Shelled out 
Spot 




No 63. Structure yi, In. Below Tread. No. 64. Structure % In. Below Tread. 

MICROPHOTOGRAPHS OF SHELLED-OUT WHEEL F. 50 DIAMETERS. 



71 




No. 67. 




No. 69. No. 70. 

MICROPHOTOGRAPHS^ OF BURNED METAL OF SCHOEN STEEL WHEEL. 
50 DIAMETERS. 



73 




BURNED METAL OF SCHOEN STEEL WHEEL 



75 



s 



OME AREAS OF CONTACT BE- 
TWEEN WHEELS OF VARIOUS 
DIAMETERS UNDER LOADS AND 
THE RAIL. 



The mutual compression between the wheel and 
the rail when under a load has an important bearing 
on the durability of both and also on the adhesion of 
the wheels when used as drivers. The investigation 
was made with various types of cars and locomotives 
to determine: the area of contact between the wheel 
and the rail; the average pressure exerted per square 
inch over this area; the accumulated pressure at 
the center of this area; the yield of the metal in both 
the rail and the wheel under the imposed load; the 
relative action of the wheel and the rail under load; 
the comparative action of wheels of different diam- 
eters, and the comparative action of steel and cast 
iron wheels. 

Through the courtesy of Mr. J. F. Deems, General 
S. M. P. of the New York Central Lines, the pre- 
liminary work involving the use of cars and loco- 
motives was done at the West Albany yards of the 
New York Central & Hudson River R.R. A concrete 
pier was built under one of the rails of a level piece 
of track to secure a firm foundation. A section 
about 10 in. long was cut out of the rail and a 
short piece with perfect contour was inserted on 
top of the pier. The car or locomotive under 
which a wheel was to be examined was run 
over this short section of rail and one wheel 
allowed to rest upon it. The wheel was then 
raised with its mate so that the section could be 



77 



removed and the top smeared with a thin coating 
of red lead. The piece of rail was then replaced 
and the wheel lowered upon it with its whole load. 
This made a spot on the red lead the size of 
the area of contact of the wheel and the rail. 
The wheel was again raised, the section of the 
rail removed, and the area of contact, as indicated 
by the spot on the red lead, transferred to 
tracing cloth. The rail was again smeared and 
replaced, and the wheel was turned through 
one quarter of a revolution and the work 
repeated. 

In the supplementary work in the laboratory a 
section of a 78-in. tire, a section of a steel wheel and 
a section of a cast iron wheel were used. One of 
these sections was fastened to the plunger of the 
testing machine and was raised and lowered on the 
heads of short sections of rails resting on the platen 
of the same. The size and shape of the contact 
area was obtained by the interposition between the 
tire and rail section of a piece of white tissue paper 
resting on a sheet of carbon paper which made 
the imprint on the white paper. 

The tests at West Albany were made with three 
cars and two locomotives. In all 32 contacts were 
obtained, and plaster of Paris casts were taken of 
the treads of the wheels at all points at which the 
contact areas were obtained. Some of the wheels 
were new, while others were partly worn, a condition 
that evidently had much to do with the shape and 
size of the spot. 

These areas were carefully measured with a 
planimeter and gave the following average results: 



78 



Wheels Used Under. 


Total Weight 

on Wheels 

in Lbs. 


Average of 
Area Contact. 


Average Weight 
per Sq. In. of 
Area in Lbs. 


Cafe Car (35 in.) .... 
Gondola (33 in.) . . . . 
Consolidation Driver (63 in.) 
Atlantic Driver (78 in.) . . 
Atlantic Trailer (48 %6 in.) . 
Dining Car (34^ in.). . . 


6,075 

14,575 
17,325 
19,995 
19,210 

9,415 


•2325 

•3775 
■3350 
.6325 

•4725 
.2600 


28,700 
40,100 
52,080 
31,820 
44,400 
37,87o 



In these tests the influence of weight and diameter 
is partially illustrated. The two wheels of the At- 
lantic engine, for example, carry about the same 
weight. The areas of contact are nearly in an in- 
verse ratio to the diameters. Comparing the wheels 
of the cafe and dining cars, the wheel with the 
heavier load has much the greater weight per sq. in. 
of area, showing that the metal does not yield in 
direct proportion to the weight, at least within the 
limits of the loads here imposed. 

In the laboratory the first series of tests made was 
to apply pressures, increasing by small increments, 
to the tread of a 36-in. steel wheel resting on an 80-lb. 
rail. The lowest load applied was 500 lbs. This 
was increased by increments of 500 lbs. up to 





« 



4* 



12 3 4 

CONTACTS OF 35-IN. STEEL-TIRED WHEEL UNDER CAF£ CAR. 
WEIGHT ON WHEEL, 6,075 LBS. 



79 




CONTACTS OF 33-INCH WORN CAST IRON WHEEL UNDER GONDOLA CAR. 
WEIGHT ON WHEEL, 14,575 LBS. 



€ii» 




1 2 

CONTACTS OF 78-IN. STEEL-TIRED DRIVING WHEEL, ATLANTIC 

LOCOMOTIVE. WEIGHT ON WHEEL, 19,995 LBS. 

20,000 lbs.; then by increments of i,ooo lbs. up to 
30,000 lbs. 

The second series was made with the same wheel 
resting on a lOO-lb. rail, starting at a load of 500 lbs. 
and increasing by increments of 500 lbs. up to 2,000 
lbs; then by increments of 1,000 lbs. up to 10,000 
lbs.; then by increments of 2,000 lbs. up to 30,000 lbs. 

The third series was made with a 78-in. tire on an 
80-lb. rail, starting at 500 lbs. and then increasing 
by increments of 500 lbs. to 2,000 lbs.; then by 



80 




1 2 

CONTACTS OF 486A6-IN. STEEL-TIRED TRAILER TRUCK WHEEL, ATLANTIC 
LOCOMOTIVE. WEIGHT ON WHEEL, 19,310 LBS. 

increments of i,ooo lbs. to 8,000 lbs.; then by 2,000 
lbs. to 30,000 lbs. and from that point by increments 
of 2,500 lbs. to 40,000 lbs. 

The fourth series was made with the 78-in. tire on 
a lOO-lb. rail, starting at 500 lbs. and increasing by 
increments of 500 lbs. to 2,000 lbs.; then by 1,000 lbs. 
to 8,000 lbs.; then by 2,000 lbs. to 30,000 lbs., and 
finally by 2,500 lbs. to 35,000 lbs. 

The fifth series was made with the section of a 
cast iron wheel ^^ ins. in diameter. This was tested 
on a lOO-lb. rail only, starting at 500 lbs.; increasing 
by 500 lbs. increments to 20,000 lbs.; then by 1,000 
lbs. to 30,000 lbs.; then by 2,500 lbs. to 40,000 lbs.; 
then by 5,000 lbs. to 150,000 lbs. 

The sixth series was made with a 36-in. steel 
wheel on a lOO-lb. rail, and started at a load of 
50,000 lbs. which was increased by increments of 
10,000 lbs. to 150,000 lbs. 

The results obtained from these tests have been 
plotted on the accompanying diagram and average 
lines drawn which show the accumulated pressure 
per sq. in. of area under the actual loads imposed, 
the lines being an average of the results obtained. 
It will be seen, on comparing the lines of the 36-in. 
steel wheel and of the 33-in. cast iron wheel, that 
there is comparatively little difference up to a load 



81 



500 Lbs. 
Av. Pressure pei* 
Sq. In. 7 143 Lbs. 
Area .07 Sq. In. 






5,000 Lbs. 

Av. Pressure per 

Sq: In. 62,500 Lbs. 

Area .08 Sq. In. 



10,000 Lbs. 

Av. Pressure per 

Sq. In. 100,000 Lbs. 

Area .10 Sq. In. 




* »• 



15,000 Lbs. 

Av. Pressure per 

Sq. In. 100,000 Lbs. 

Area .15 Sq. In. 




20,000 Lbs. 

Av. Pressure per 

Sq. In. 86.956 Lbs. 

Area .23 Sq. In. 




25,000 Lbs. 

Av. Pressure per 

Sq. In. 92,555 Lbs. 

Area .27 Sq. In. 




30,000 Lbs. 

Av. Pressure per 

Sq. In. 96,774 Lbs. 

Area .31 Sq. In. 



CONTACTS BETWEEN 36-IN. STEEL-TIRED WHEEL AND 80-LB. RAIL. 



500 Lbs. 

Av. Pressure per 

Sq. In. 16,666 Lbs. 

Area .03 Sq. In. 



5,000 Lbs. 

Av. Pressure per 

Sq. In. 62,500 Lbs. 

Area .08 Sq. In. 



10,000 Lbs. 

Av. Pressure per 

Sq. In. 71,428 Lbs. 

Area .14 Sq- In. 



16,000 Lbs 

Av. Pressure per 

Sq. In 94,117 Lbs. 

Area .17 Sq In. 



20,000 Lbs. 

Av. Pressure per 

Sq. In. 105,263 Lbs. 

Area .19 Sq. In. 




26,000 Lbs. 

Av Pressure per 

Sq. In. 108,333 Lbs. 

Area .24 Sq. In. 




30,000 Lbs. 

Av. Pressure per 

Sq. In. 115,384 Lbs. 

Area .26 Sq. In. 



CONTACTS BETWEEN 36-IN. STEEL-TIRED WHEEL AND 100-LB. RAIL. 



82 



^.^ 'sm^ mi$» 



500 Lbs. 

Av Pressure per 

8q. ln.25 000 Lbs. 

Area 02 Sq In 



5,000 Lbs 

Av. Pressure per 

Sq. In. 62,500 Lbs." 

Area .08 Sq. In. 



10,000 Lbs. 

Av Pressure per 

Sq In 71,428 Lbs. 

Area 14 Sq. m 




16 000 Lbs. 

Av Pressure per 

Sq In 80,000 Lbs 

Area 20 Sq In 




20,000 Lbs. 

Av Pressure per 

Sq. In. 90,909 Lb&. 

Area .22 Sq fn. 




26,000 Lbs. 

Av. Pressure per 

Sq. In 100,000 Lbs. 

Area .26 Sq. In. 




30,000 Lbs. 

Av Pressure per 

Sq. In 100,000 Lbs. 

Area 30 Sq In 





35,000 Lbs. 

Av. Pressure ^ar 

Sq. In, 102,941 Xbs. 

Area .34 Sq In 



40,000 Lbs 

Av. Pressure per 

Sq. Irt. 111,111 Lb« 

Area 36 Sq. In 



CONTACTS BETWEEN 78-IN. STEEL-TIRED WHEEL AND 80-LB. RAIL. 



300 Lbs. 

Av. Pressure per 

Sq In 16,666 Lbs. 

Area .03 Sq. In. 




10,000 Lbs. 

Av, Pressure pet 

Sq. In 83 333 Lb» 

Area 12 Sq In. 



16,000 Lbs. 

Av Pressure per 

Sq. In. 106,666 Lb» 

Area 15 Sq In. 



20,000 Lbs 

Av Pressure per 

Sq In 105^263 Lbs 

Area 19 Sq In 




26,000 Lbs. 

Av. Pressure per 

Sq. In. 100,000 Lbs. 

Area .26 Sq. In. 




30,000 Lbs. 

Av. Pressure per 

Sq. In. 103,448 Lb?. 

Area .29 Sq. In. 



85,000 Lbs 

Av Pressure per 

Sq. In, 109,375 Lbs 

Area .32 Sq in 



CONTACTS BETWEEN 78-IN. STEEL-TIRED WHEEL AND 100-LB. RAIL, 



83 



50,000 Lbs. 

Av. Pressure per 

Sq. In. 131,578 Lbs. 

"Area .38 Sq. In. 



60,000 Lbs. 

Av. Pressure per 

Sq. In. 127,659 Lbs 

Area .47 Sa. In. 



70,000 Lbs. 

Av. Pressure per 

Sq. In 129,629 Lbs. 

Area .54 Sq. In. 




80,000 Lbs. 

Av. Pressure per 

Sq. In. 137,288 Lbs. 

Area .59 Sq. In. 



90,000 Lbs. 

Av Pressure per 

Sq. In. 135,757 Lbs. 

Area .66 Sq. In 



100,000 Lbs 

Av Pressure per 

Sq. In. 138,888 Lb»> 

Area 72 Sq. In 




110,000 Lbs. 

Av. Pressure per 

Sq. In. 137,500 Lbs 

Area .80 Sq. In. 




120,000 Lbs. 

Av Pressure per 

Sq In, 141,176 Lbs 

Area .85 Sq. In 



CONTACTS BETWEEN 36-IN. STEEL WHEEL AND 100-LB. RAIL. 

of 22,500 lbs., after which the load per sq. in. increases 
more rapidly with the cast iron wheel than with the 
steel wheel. At a load of 37,500 lbs. there is a 
marked breaking down of the metal in the cast iron 



84 





130,000 Lbs. 

Av. Pressure per 

Sq. In. 141,304 Lbs 

Area .92 Sq. In, 




140,000 Lbs. 

Av. Pressure per 

Sq. In 137,254 Lbs. 

Area 1.02 Sq. In. 



150,000 Lbs. 

Av. Pressure per 

Sq In. 144 230 Lbs. 

Area 1.04 Si), In. 

CONTACTS BETWEEN 36-IN. STEEL WHEEL AND 100-LB. RAIL. 

wheel showing that the crushing strength has been 
exceeded. 

A tentative explanation of this phenomenon is 
that the hard chilled cast iron wheel is practically 
unyielding and that, when the load is imposed, the 
whole of the compression takes place in the rail. The 
area of contact is small and the average pressure per 
sq. in. of area is high. The yield in the rail holds, 
for a time, against the increasing load, thus cutting 
down the size of the area between 22,500 lbs. and 
40,000 lbs. The wheel itself then takes a permanent 
set, increasing the area of contact very rapidly and 
lowering the average. In the case of the steel wheel, 
yielding takes place in both the wheel and the rail, 



85 






500 Lbs. 
Av. Pressure per 
Sq. In. 9,090 Lbs. 
Area .055 Sq. In. 




4,500 Lbs. 

Av. Pressure per 

Sq. In. 50,000 Lbs. 

Area .09 Sq. In. 




13,500 Lbs. 

Av. Pressure per 

Sq. In. 96,428 Lbs. 

Area .14 Sq. In. 






17,500 Lbs. 

Av. Pressure per 

Sq. In. 94.444 Lbs. 

Area .18 Sq. In. 






1,000 Lbs. 

Av. Pressure per 

Sq. In. 14,285 Lbs. 

Area .07 Sq. In. 




6,000 Lbs. 

Av. Pressure per 

Sq. In. 54,545 Lbs. 

Area .11 Sq. In. 



w 



14,500 Lbs. 

Av. Pressure per 

Sq. In. 96.666 Lbs 

Area .15 Sq. In. 




19,000 Lbs. 

Av. Pressure per 

Sq. In. 100,000 Lbs. 

Area .19 Sq. In. 



-•«t 



2,500 Lbs. 
Av. Pressure per 
Sq. In. 33,333 Lbs. 
Area .075 Sq. In. 




10,000 Lbs. 

Av. Pressure per 

Sq. In. 83,333 Lbs. 

Area .12 Sq. In. 




15,000 Lbs. 

Av. Pressure per 

Sq. In 93,750 Lbs 

Area .16 Sq. In. 



3,500 Lbs. 

Av. Pressure per 

Sq. In. 43,750 Lbs. 

Area .08 Sq. In. 






11,500 Lbs. 

Av. Pressure per 

Sq. In. 88,461 Lbs. 

Area .13 Sq. In. 



16,500 Lbs. 

Av. Pressure per 

Sq. In. 97,058 Lbs. 

Area .17 Sq. In. 




25,000 Lbs. 

Av. Pressure per 

Sq In 125,000 Lbdl 

Area .20 Sq. In. 



27,000 Lbs. 

Av. Pressure per 

Sq. In. 128,571 Lbs. 

Area .21 Sq. In. 




30,000 Lbs. 

Av. Pressure per 

Sq. In. 130,434 Lbs. 

Area .23 Sq. In. 



28,000 Lbs. 

Av. Pressure per 

Sq. In. 127,272 Lbs 

Area .22 Sq In. 

CONTACTS BETWEEN ,33-IN. CAST IRON WHEEL AND 100-LB. RAIL. 



32,500 Lbs. 

Av. Pressure per 

Sq. In. 130,000 Lbs. 

Area .25 Sq. In. 



35,000 Lbs. 

Av. Pressure per 

Sq. In. 134,615 Lbs. 

Area .26 Sq. In. 



86 



with the result that an equihbrium is estabhshed on 
a smaller area and the actual breaking down of the 
metal occurs under a higher pressure. 

In the case of the cast iron wheel it will be 
noted that the curve of average pressure shows a 
break and yield of the material at a load of 27,000 
lbs., though it rises again and makes a second com- 
plete break at 37,500 lbs., from which there is no 
recovery. In the case of the steel wheel the break- 
down does not occur until a load of 50,000 lbs. is 
reached, and even then there is a gradual and prac- 
tically uniform advance to 150,000 lbs. 

In the tests of both the cast iron wheel and the 
steel wheel, the permanent set was all in the rail. 
Both wheels were carefully examined with a micro- 
scope after the load of 150,000 lbs. had been imposed 
and the tests were completed, and no appearance 
of yielding or cracking of either could be detected. 
The rail, on the other hand, showed signs of a perma- 
nent set under a load of 20,000 lbs., and this set 
increased with the increasing loads. The rail was 
examined immediately after applying loads of 12,000, 
15,000, 25,000, 30,000, 35,000, and 40,000 lbs. The 
spot or depression left by the wheel could be seen 
after the 20,000 lbs. load had been imposed, but not 
before. 

The difference between the areas of contact of the 
wheels under cars and locomotives and the wheels 
tested in the laboratory, in which the area was 
larger, is probably due to the fact that the wheels 
under the cars and locomotives were worn somewhat 
hollow and so fitted the rail head to a greater extent. 
In service, however, the swinging of the wheels from 



87 




37,500 Lbs. 

Av. Pressure per 

Sq. In. 138,888 Lbs. 

Area .27 Sq. In. 




40,000 Lbs. 

Av. Pressure per 

Sq. In. 137,777 Lbs. 

Area .29 Sq. In. 




45,000 Lbs. 

Av. Pressure per 

Sq. In. 136,363 Lbs. 

Area .33 Sq. In. 




r*^t*/ 



50,000 Lbs. 

Av. Pressure per 

Sq. In. 1.21,951 Lbs. 

Area .41 Sq. In. 




55,000 Lbs. 

Av.. Pressure per 

Sq. In. 119,565 Lbs. 

Area .46 Sq. In. 




59,000 Lbs. 

Av. Pressure per 

Sq. In- 118,000 Lbs. 

Area .50 Sq. In. 




65,000 Lbs. 

Av. Pressure per 

Sq. In. 118 181 Lbs. 

Area .55 Sq. In. 



70,000 Lbs. 

Av. Pressure per 

Sq. In. 118,644 Lbs. 

Area .59 Sq. Jn. 



75,000 Lbs. 

Av, Pressure per 

Sq In. 122,950 Lbs. 

Area .61 Sq. In. 



CONTACTS BETWEEN 33-IN. CAST IRON WHEEL AND 100-LB. RAIL. 



88 



s^f 




80,000 Lbs. 

Av. Pressure per 

Sq. \n. 126,983 Lbs. 

Area .63 Sq. In. 



85,000 Lbs. 

Av. Pressure per 

Sq. In. 116,666 Lbs 

Area .72 Sq. In. 



90,000 Lbs. 

Av Pressure per 

Sq. In. 121,621 Lbs. 

Area .74 Sq. In. 




6 

95,000 Lbs. 

Av. Pressure per 

Sq. In. 121,794 Lbs 

Area 783q. (n. 



100,000 Lbs. 

Av, Pressure pep 

6q. In. 120,481 Lbs. 

Area .83 Sq. In. 



105,000 Lbs. 

Av. Pressure pee 

Sq. In. 117,977 Lbs. 

Area .89 Sq In. 




110,000 Lbs. 

Av. Pressure per. 

Sq. In. 118,279 Lbs. 

Area .93 Sq. In. 



115,000 Lbs. 

Av. Pressure per- 

Sq. In. 116,161 Lbs. 

Area .99 Sq. In. 



120,000 Lbs. 

Av. Pressure per 

Sq In. 115,384 Lbs. 

Area 1.04 Sq. In. 



CONTACTS BETWEEN 33-IN. CAST IRON WHEEL AND 100-LB. RAIL. 







125,000 Lbs. 

Av. Pressure per 

Sq. In. 119,047 Lbs. 

Area 1.05 Sq. In. 




130,000 Lbs. 

Av. Pressure per 

Sq. In. 117,117 Lbs. 

Area 1.11 Sq. In. 




135,000 Lbs. 

Av. Pressure per 

Sq. !n. 119,469 Lbs. 

Area 1.13 Sq. In. 




140,000 Lbs. 

Av. Pressure per 

Sq. In. 130,434 Lbs. 

Area 1.15 Sq. In. 



CONTACTS BETWEEN 33-IN. CAST IRON WHEEL AND 100-LB. RAIL. 

one side of the track to the other brings the projec- 
tions on the outer edge of the rim against the rail, 
undoubtedly causing a much higher load to be put 
on a smaller area of contact than was applied in the 
laboratory. 

The permanent set taken by the rail at so low a 
load as 20,000 lbs. raised the question of the 



90 



maximum pressure imposed at the center of the area 
of contact. It was assumed that when the wheel 
first touched the rail the area of contact would be a 
mathematical point if both surfaces were perfectly 
smooth and true. As the load is increased the 
metal in both the wheel and rail yields and the area 
of contact increases. This increase is from the center 
out to the edge, and the pressure per unit of area is 
evidently at a maximum at the center and decreases 
to nothing at the edge. In order to estimate approx- 
imately the maximum pressure it was assumed that 
the metal in the area on which a load had once been 
imposed always sustained it, and by building up 
from the center by increments the final load was at- 
tained. Take the case of the 36-in. steel-tired wheel 
on the lOO-lb. rail. An area of .03 sq. in. sustained the 
initial load of 500 lbs., with an average pressure of 
16,666 lbs. per sq. in. By increasing this load to 5,000 
lbs. the area is increased to .08 sq. in. If this extra 
4,500 lbs. which was applied be considered as loaded 
uniformly over the whole area, there would be an 
average increase of pressure of 56,250 lbs. per sq. in. 
or 56,250+16,666 = 72,916 lbs. per sq. in. on the 
original .03 sq. in. which carried the initial load of 
500 lbs. This assumption runs the load up to an 
exceedingly high limit, possibly too high, as it gives 
a pressure of more than 170,000 lbs. per sq. in. at the 
center of the area of contact, with a load of 20,000 lbs. 
In considering the results obtained in this investi- 
gation, it must be borne in mind that the areas of 
contact were all obtained under static loads. Run- 
ning conditions must necessarily be more severe 
and impose higher stresses. In an investigation 



91 





145,000 Lbs 

Av Pressure per 

Sq. la, 123,931 Lbs, 

Area 1.17 Sq. In. 



150,000 Lbs. 

Av. Pressure per 

Sq. In. 124,049 Lb» 

Area 1.21 Sq. In. 



CONTACTS BETWEEN 33-IN. CAST IRON WHEEL AND 100-LB. RAIL. 

conducted several years ago it was found that the 
stresses in truck and body bolsters, while a car is in 
motion, are from 20 to 50 per cent, more than the 
stresses due to static loads alone. If this is true for parts 
located above the springs, there must certainly be an 
equal or greater increase at the point of contact be- 
tween the wheel and the rail. Then, too, the blows 
received from passing over low joints or worn frogs, 
will raise the pressure between the wheel and the 
rail to a point which the tests under static loads have 
shown to be excessive. For example, the wheels, 
under a car of 100,000 lbs. capacity with a 10 per 
cent, overload, carry an approximate static load of 
18,750 lbs. each. A drop of tV in. is equivalent to a 
blow of about 97 foot lbs. If the drop is checked by 
a yield in the rail of three-eighths of the amount of 
the drop (tIf in.) the pressure on the rail will amount 
to 50,000 lbs. This is certainly excessive. 

Comparing the steel and cast iron wheels, it ap- 
pears that no damage was done to either wheel under 



92 



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z.tM/p /yy f^uA/DS 



DIAGRAM SHOWING THE RELATION BETWEEN WEIGHTS ON WHEELS, AND 
THAT ON THE AREA OF CONTACT BETWEEN THE WHEEL AND THE RAIL. 

a static load of 150,000 lbs. If the two wheels are 
subjected to the pounding action of service, however, 
the result cannot fail to be the earlier disintegration 
of the harder, more unyielding and more brittle 
material. Exact comparative data along this line 
are not yet available. 



93 



The conclusions to be drawn from this part of 
the work may be summed up as follows : 

The average pressure imposed on the metal of the 
wheel and rail is within safe limits at low loads, but 
when a load of 20,000 lbs. is reached the elastic limit 
of the metal is passed and a permanent set appears 
in the rail. 

The accumulated pressure at the center of the area 
of contact is excessive at comparatively small loads, 
and is only prevented from doing injury by the support 
of the surrounding metal. How far this compression 
extends into the body of the two pieces of metal in 
contact is not known, but presumably it extends down 
to the base of the rail and into the hub of the wheel. 

Under a static load the rail yields first, owing, 
probably, to the fact that the metal of the surface of 
the head of the rail is not as well supported by the 
metal below as in the case of the wheel. 

The effect of difference of diameter in wheels carry- 
ing the same load is insignificant and is only appreci- 
able when the difference is great. Hence it is imma- 
terial so far as stresses on the wheel or rail are 
concerned, whether small or large wheels, within the 
limits of practice, are used. 

A hard, unyielding cast iron wheel inflicts more 
damage on the rail than a steel wheel, and the wear 
of the rail will be greater with the cast iron wheels 
than with the steel wheels. 

It is probable that the reason why the damage 
that would be expected from heavy wheel loads in 
service does not immediately appear, is that the rail, 
by bending under the passing wheel, increases the 
area of contact and thus relieves the surface stresses. 



94 



c 



OEFFICIENTS OF FRICTION BE- 
TWEEN WHEELS AND RAILS. 
TRACTIVE VALUES. SKIDDING 
AND SLIPPING. 



The resistance of a wheel to slipping on the rail 
depends upon two causes frequently confused, but 
which are to be considered separately. These are 
friction and abrasion. 

Frictional resistance is due to the roughnesses of 
the two surfaces in contact, and may be compared to 
the lifting of the weight to be moved over the suc- 
cessive inequalities of the surface on which it rests. 
Abrasion, on the other hand, involves the removal 
or cutting away of the particles of the masses in 
contact. The slipping of a wheel, such as would 
produce a flat spot, involves both frictional resist- 
ance and abrasion. If there was no slipping of 
the wheel on the rail there would be no wear, pro- 
vided the rolling action did not produce sufficient 
pressure on any one point to crush the metal or 
cause it to flow. But there is always more or less 
slip even on a straight line. 

There are two kinds of slipping to which car 
wheels may be subjected. One is the skidding 
action due to the locking of the wheels by the brake- 
shoes. The other form occurs when the driving 
wheels of electric motor cars, for instance, are turned 
faster than the corresponding rate of motion of the 
car and the whole periphery of the wheel slides 
over the rail. In order to determine whether the 
resistances to these two kinds of slipping were the 
same certain experiments were made. 



95 




ARRANGEMENT OF APPARATUS TO TEST THE FRICTIONAL RESISTANCE OF 
CAR WHEELS TO SKIDDING. 

The apparatus was designed to produce, as nearly 
as possible, the actual conditions of track work. 

Two pieces of steel rails of 75 lbs. section, one of 
which had been worn smooth in service, the other a 
piece of new rail, together with a section of a steel 
wheel and a section of a cast iron wheel, with the 
treads of both smooth and free from imperfections, 
were used for the tests. The testing machines were 
made by Tinius Olsen & Co., one with a capacity of 
100,000 lbs. and the other a capacity of 50,000 lbs. 

The apparatus is shown in the accompanying 
illustrations for the skidding movement. The wheel 
section was set on the rail and loaded by the 100,000 
lbs. capacity machine. It was then slipped over the 
rail by a pull on the connection rod reaching to 
the other machine which measured the amount of 
the pull required to slip the wheel on the rail. 



96 




PL/:iT£A/ or rssrwc M^cmvs 



ARRANGEMENT OF APPARATUS FOR TESTING THE FRICTIONAL RESISTANCE 
OF CAR WHEELS TO SPINNING. 

In loading the wheel, the pressure was applied 
through a plate resting on two rollers. In this way 
the friction, except that between the wheel and the 
rail, was reduced to practically nothing. 

For the spinning motion, the bearing plate above 
the rollers was made convex and the bottom plate 
resting on the top of the wheel was made concave, 
both surfaces being concentric with the tread of the 
wheel. A pull on the wheel, therefore, caused it to 
roll under the bearing plate as though it were re- 
volving on its own center. The arrangement of this 
is clearly shown in the diagram. 

The force required to move the wheel on the rail 
was weighed by a bell crank with a knife-edge bear- 
ing, resting on a heavy casting attached to the bed 



97 



plate of the small testing machine. The vertical arm 
was attached to the pull rod and the end of the 
horizontal arm had a bearing on a wedge or knife 
edge that was forced down by the platen of the 
machine. 

The wheel section was placed in position on the rail 
and weighted with a predetermined load. Pressure 
was then applied to the wedge on the small machine. 
This pressure was transferred through the bell crank 
as a pull on the connecting rod. When slipping 
occurred, the event was marked instantly by the drop 
of the beam of the small machine. The movement of 
the wheel over the rail usually amounted to about 
^ in. As the object of the investigation was to 
determine the friction at rest no attempt was made 
to measure the pull after the first slip occurred. 
This was markedly less than that required to start 
the movement from a state of rest. 

Separate tests were made with steel and cast 
iron wheels on the old and new rails, for both the 
skidding and spinning motions. In loading the 
wheels, the weights were increased by regular incre- 
ments of 2,000 lbs. up to 30,000 lbs. Three tests 
were made with each loading and for each condition 
of wheel movement. The average of the three tests 
in each case is given in the accompanying table. 

There was so little difference in the pull required 
to slip the wheels on the old and new rails that an 
average of the results obtained is given as the resist- 
ance to spinning and skidding of the two wheels on 
a steel rail. 

The table shows that the resistance to spinning of 
the steel wheel is somewhat greater than that of the 



98 



COEFFICIENTS OF FRICTION BETWEEN WHEELS 
AND RAILS. 



Load on Wheel 


Kind o£ Motion 


Spinning 


Skidding j 


in Lbs. 








Steel 


Cast Iron 


Steel 


Cast Iron 




Wheel. 


Wheel. 


Wheel. 


Wheel. 


2,000 


•259 


■243 


.285 


.287 


4,000 


.240 




215 




254 


•259 


6,000 


•234 




208 




245 


■254 


8,000 


.228 




206 




246 


.242 


10,000 


.215 




204 




238 


•233 


1 2,000 


.212 




205 




237 


.223 


14,000 


.207 




199 




233 


.226 


16,000 


.204 




196 




232 


.219 


18,000 


.204 




198 




231 


.219 


20,000 


.201 




194 




236 


.220 


22,000 


.205 




191 




238 


.223 


24,000 


.204 




192 




235 


.224 


26,000 


.205 




189 




232 


.223 


28,000 


•203 




186 




236 


.217 


30,000 


.203 




183 




234 


.214 



cast iron wheel, a fact which is brought out more 
forcibly in the table of coefficients of friction, in 
which the coefficient of the steel wheel is invariably 
higher than that of the cast iron. 

It also appears from this table that the coefficient 
of friction of the steel wheel decreases as the load is 
increased, up to a pressure of about 15,000 lbs., after 
which it is practically constant. The coefficient of 
friction of the cast iron wheel decreases rather rapidly, 
like that of the steel wheel, up to a load of 15,000 
lbs., after which it falls away slowly, though a 
tendency to decrease with the increase of load is 
manifest. 

As regards skidding, the values of the coefficients 
of the two wheels bear the same relation to each other 

LOFC 



99 



as they do for spinning. The coefficient of resistance 
is greater for the steel wheel than for the cast iron 
wheel, and there is the same falling off in the value 
of the coefficient as the load is increased up to about 
15,000 lbs., after which that of the steel wheel is 
nearly constant, while that of the cast iron wheel 
continues to fall away slowly. It would be difficult 
to explain these phenomena without the data ob- 
tained in the investigations previously described, 
made to determine the area of contact between the 
wheel and the rail, and the relative rate of abrasion 
of the steel and cast iron wheels on the emery wheel. 
The results of those investigations also serve to ex- 
plain why the coefficient for a skidding wheel is 
higher than the coefficient for a wheel that is spinning. 
In the case of the cast iron wheel, it was shown in 
the preceding chapter that the imposition of a heavy 
load caused a breaking down of the metal in the 
rail at a certain point, while no such failure occurred 
with the steel wheel under the same load. The cast 
iron wheel being rigid, inelastic and incompressible 
on the tread, was forced down into the metal of the 
rail, causing the rail to do all of the yielding needed 
to produce the area of contact obtained, with the 
result that it was soon compressed beyond its elastic 
limit and given a permanent set. The steel wheel 
yielded as well as the rail, thus relieving the rail of 
a part of its compression and increasing the area of 
contact. This behavior of the two wheels explains 
in part the results obtained in these tests. In ad- 
dition, it must be remembered that the normal co- 
efficient of friction is greater between steel and steel 
than it is between cast iron and steel. 



When the cast iron wheel is loaded on the rail it 
indents the rail, in proportion to the pressure ap- 
plied, without being distorted itself. If, then, it is 
turned, as by a motor, it simply revolves in the concave 
depression in the rail, without undergoing any de- 
formation itself and with no resistance other than 
that of overcoming the friction between the surfaces 
of the wheel and rail. The steel wheel, on the 
other hand, is itself compressed as well as the rail, 
so that when it is turned a continuous progressive 
compression of the tread is set up, equal to the 
amount of the original compression. Hence, the 
resistance to turning will be equal to the frictional 
resistance plus that set up by this compression. 

It was shown that the cast iron wheel was cut 
away much more rapidly under the emery wheel 
than were the steel tires and wheels. In the tests 
for skidding, the loads were successively applied 
without readjusting the wheel on the rail, with 
the result that the steel wheel was skidded about 
i^ in. and the cast iron wheel about i in. This 
was done under loads increasing from 2,000 lbs. 
up to 30,000 lbs. Under this treatment the steel 
wheel developed a slid-flat spot about fV in. long, 
and the cast iron wheel a spot about | in. long. In 
both cases the rail was spotted and the metal was 
rolled up in folds, indicating the direction of the 
motion of the wheel. The piece of rail used with 
the steel wheel was spotted for a distance of about 
l| in., while the piece used with the cast iron wheel 
was spotted for a length of about i| in. This 
abrasion of the cast iron wheel probably accounts 
for the lower resistance to skidding as compared with 



the steel wheel. For the same weight and for the 
same distance of skidding, the amount of metal 
abraded from the cast iron wheel was in almost 
exactly the same ratio to that removed from the steel 
wheel, as is shown in the diagram of abrasion tests. 

It will be remembered that, for the lower wheel 
loads, the investigation of contact areas showed that 
there was comparatively little difference between the 
areas obtained with cast iron wheels and with steel 
wheels, and that it was inferred that the total com- 
pression of the metal was approximately the same 
in both cases. Under these circumstances it would 
be expected that, if the power required to distort the 
metal of a steel rail and tire were the same, the 
resistance to skidding of the steel wheel and the cast 
iron wheel would also be the same. But, owing to 
the more rapid abrasion of the cast iron wheel, as 
soon as it begins to skid it wears, and by thus in- 
creasing the area of contact it lessens the depression 
of the rail, decreases the amount of metal to be 
distorted, lowers the resistance to the motion, and 
makes the coefficient of friction of skidding less on 
the cast iron wheel than on the steel wheel. 

This depression of the rail due to the imposition of 
the wheel load accounts for the higher coefficient of 
friction obtained with a skidding wheel than with a 
spinning wheel. With a wheel spinning there is no 
continuous deformation of the metal of the rail to be 
effected. In skidding there is a depression of the 
rail to be carried forward like a wave, which natural- 
ly raises the resistance and makes the coefficient 
greater than where slipping over one spot alone 
takes place. 



While it is not safe to draw rigid conclusions from 
the limited amount of data obtained, it does appear 
that inasmuch as the steel wheel offers greater re- 
sistance to spinning it is better adapted for use as the 
driving wheel of an electric car than the cast iron 
wheel; and further, its higher coefficient of friction 
renders it less liable to skidding. 

This matter of wheels skidding, with the conse- 
quent development of flat spots on the tread, was 
considered of enough importance to warrant further 
investigation. 

It has been noted by many other investigators 
that steel wheels do not flatten as readily as cast iron 
wheels. By some this is attributed to the fact that 
small flat spots once formed on the tread of a steel 
wheel may be rolled out, whereas they have a tend- 
ency to grow larger on cast iron wheels. The 
abrasion and skidding tests which have been made 
seem to show, however, that it is the lower resistance 
to grinding of the cast iron wheel that accounts for 
the more rapid development of these flat spots. 

To briefly recapitulate, these tests showed that the 
rate of grinding of the first | in. below the tread was 
about 4.64 times as fast in the cast iron wheel 
as in the Schoen steel wheel. For the second 
I in. the ratio became 6.37 and for the third | in. 
15.93, showing the rapid decrease of wearing resist- 
ance of the cast iron wheel below the surface. In 
the skidding tests in the laboratory the effects were 
confined to the metal close to the surface, and it 
was found that, with the same amount of skidding, 
the amount of metal removed was about 5.12 times 
as great on the cast iron wheel as on the steel wheel. 



103 



A further check on these figures was afterwards ob- 
tained by taking the time required to remove approxi- 
mately the same amount of material from the treads 
of cast iron and steel wheels in a wheel grinding 
machine. It was found that it took from four to 
five times as long to grind down the steel wheels as 
it did to grind the cast iron wheels. In all of the 
foregoing investigations the metal of the wheel under 
test was kept cool, either by a stream of water 
or by doing the work so slowly that natural radia- 
tion counteracted the tendency to heat, and the 
temperature of the metal was not raised above lOO 
deg. Fahr. 

For the purpose of ascertaining whether the re- 
sults of these investigations were comparable with 
the results obtained in actual railroad service, when 
the wheels were locked and skidded under a car, 
series of tests were made by skidding the wheels 
under a loaded car. 

Through the courtesy of the New York, Ontario 
& Western Railroad a piece of track and a suitable box 
car were supplied for the tests. One pair of wheels 
and axle were removed from under the car, and 
replaced by an axle on which a Schoen steel wheel 
and a new cast iron wheel had been pressed. These 
wheels were ^^^ in. and ^^ in. in diameter, respect- 
ively. This pair of wheels was placed at the end of 
the car, and was fitted with two brake-beams, so that 
twice the usual brake-shoe pressure could be applied 
on the wheels. By this means the wheels could 
be held in a fixed position throughout a run. But 
it was more difficult to hold the wheels at low speed 
than at high speed. 



104 



The car was loaded until the weight on the pair of 
wheels to be tested was exactly 24,000 lbs. The car 
was then hauled back and forth over a piece of track 
1,850 ft. long. The brake was set and the wheels skid- 
ded for the whole distance. The car was hauled at 
two speeds, namely, three and twelve miles an hour. 

When the car was hauled at a speed of three miles 
an hour, flat spots were made on the steel wheel about 
.30 sq. in. in area, while the spots formed on the cast 
iron wheel were .80 sq. in. in area. These areas 
correspond to diameters of about f in. and i in. 
respectively, though the spots on the cast iron wheel 
were elongated to about i| in., which indicated some- 
what more metal removed. The volume of metal 
abraded from the cast iron wheel was about 5I times 
greater than that from the steel wheel. 

While the movement was slow the wheels remained 
cool. But when the speed was increased to twelve 
miles an hour heating took place and the cutting 
was more rapid on the steel wheel. 

For the first 1,850 ft. run the areas of the flat spots 
produced at a speed of 12 miles an hour averaged 
8.125 ^^- ^^^' ^^ th^ steel wheel and 4.445 sq. ins. on 
the cast iron wheel. The estimated amount of 
metal worn away was 4.63 times as much with the 
steel wheel as with the cast iron wheel. 

When the skidding was continued the rate of wear 
increased very rapidly with the cast iron wheel, while 
there was little increase with the steel wheel. At 
the end of the run of 3,700 ft. the area of the flat 
spot on the steel wheel was 8.43 sq. ins., an increase 
of .305 sq. in., while the area of the spot on the cast 
iron wheel was 5.72 sq. ins., an increase of 1.275 ^^- ^^• 



105 



From this it appears that the cast iron wheel wore 
away more rapidly than the steel wheel after the 
hard surface metal had been broken through. 

The indications are that in skidding a short dis- 
tance at low speed a cast iron wheel is more apt to 
develop a flat spot than is a steel wheel. On the 
other hand, if the skidding continues for some dis- 
tance at a high speed, the wheel becomes heated and 
then the steel wheel is the first to yield, unless the 
surface chill of the cast iron wheel has already been 
worn through. 



io6 



i: 



ATERAL THRUST OF WHEELS 
AGAINST THE RAILS. BREAK- 
ING STRESSES OF WHEEL 
FLANGES. 



It is generally admitted that cast iron wheels under 
high capacity cars are giving unsatisfactory service 
and, because of their inherent lack of strength, are 
a source of danger. Prior to 1905 little was known 
of the strength of these wheels except that they had 
a shorter life and gave far more trouble from flange 
breakage under the high capacity cars than they 
had under cars with a capacity of only 60,000 lbs. 
In that year Professor Goss made some tests in 
the laboratory of Purdue University to ascertain 
the strength of the flanges of cast iron wheels. 

Six new wheels and one wheel which had broken 
in service were tested. The wheel to be tested was 



rm 




APPARATUS FOR TESTING STRENGTH OF WHEEL FLANGES. 



107 



TABLE OF 


BREAKING STRESSES OF WHEEL FLANGES. 


No. 

of 

Test 

I 


Breaking 
Load. 
Lbs. 


No. of WheeL 


Point of Application 
of Load. 


Remarks. 


52,850 


M. C. B. 19413 


Between brackets 




2 


47.750 


" 


Opposite " 




3 


49,350 


" 


Between " 




4 


53400 


" 


Opposite " 




5 


62.850 


M. C. B. 19410 


Between " 




6 


48,700 


" 


Opposite " 




7 


58,250 


K 


Between " 




8 


58,000 


" 


Opposite " 




9 


74,850 


M. C. B. 19254 


Between " 




lO 


72,200 


" 


Opposite " 




II 


87,000 


" 


Between " 




12 


68,550 


" 


Opposite " 




13 


99,300 


(e) 650 lbs. 


Between " 




14 


100,000 


" 


Opposite " 




15 


105,900 


" 


Between " 




16 


68,200 


" 


Opposite " 


[Wheel 


17 


79,350 


" 


" " 


J broke 
1 throuffh 


18 


52,300 


19558 


Between " 


[rim. 




111,600 


(f) 700 lbs. Tape i 


Opposite " 




19 


87,000 


" 


Between " 




20 


109,900 


(1 


Opposite " 




21 

22 


98,900 


, . ( 1904 M. C. B. ) 
^^^ \ 700 lbs. Tape 2 J 


" 




23 


98,900 


" 


<( (( 





mounted on a strong mandrel secured to the base 
of the testing machine in such a manner that it could 
not slip, and a punch was forced down against the 
flange in the same way that the rail presses against 
it in service. Pressure was applied until the flange 
broke. The general arrangement of the apparatus 
is shown in the illustration on page 107. The punch 
A was bolted to the head of the machine. It was 
prevented from springing away from the work by 
a roller bearing against a bracket which was bolted 
to the platen of the machine. 



108 



AVERAGES OF BREAKING STRESSES OF WHEEL 
FLANGES. 



Average Breaking 
Load. Lbs. 


No. of Wheel. 


Remarks. 


50.837 
56,950 
75.650 

52,300 


19.413 
19,410 

19.254 
19.558 


Taken from service 

a <i <i 
i< (( (( 

Broken wheel taken 
from service. j 



Three of the wheels tested, Nos. 19,413, 19,410 
and 19,254, were new wheels of M, C. B. dimen- 
sions. The fourth, No. 19,558, was a piece of a 
wheel which had broken in service. In addition to 
these specimens three new wheels were tested which 
were especially designed to give increased flange 
strength. These were marked 

(e) 650 lbs. 

(f) 700 lbs. Tape i 

(g) 700 lbs. " 2 

Wheels (e) and (f ) were of a reinforced flange design 
and wheel (g) was the then proposed Standard of 
the M. C. B. Association with reinforced flange. 

Four tests were made with each of the M. C. B. 
standard wheels, and from two to four tests with 
each of the others. The results are given in detail 
in the Table of Breaking Stresses of Wheel Flanges. 

Three of the tests made on the (e) wheel showed a 
flange strength of approximately 100,000 lbs., while 
the fourth test (16) gave only 68,200 lbs. In view 
of this wide difference an attempt was made to get 
a fifth test from this wheel by applying pressure 
to the flange midway between two of the breaks 



109 



previously made, with the result that the wheel broke 
through the rim at 79,350 lbs. 

Test No. 18 was made on a piece of a wheel 
which had broken in service and the holding device 
which had been employed for new wheels had to 
be supplemented by additional clamping for the 
test. For this reason it is not known whether the 
results obtained from the fragments are entirely com- 
parable with those obtained from the whole wheels. 

It will be seen from these tests that not only were 
there wide variations in the strength of flanges of 
wheels of similar design but in different parts of 
the flange of the same wheel. Reinforcing the flange 
added to the strength, but even in individual wheels 
thus reinforced there is a variation from 68,200 lbs. 
to 105,900 lbs. in the breaking strength. 

These tests cover practically all that is known of 
the strength of the cast iron wheel to resist the 
thrust on the rail. In order to ascertain approxi- 
mately the relative strength of the steel wheel under 
similar conditions a Schoen wheel was tested in 
the same way. The work was done under a power- 
ful hydraulic press and the flange broke ofi^ under a 
load of 526,612 lbs. This was more than 4.7 times 
the load required to break the strongest part of the 
reinforced flange and more than 1 1 times the load re- 
quired to break the weakest of the standard flanges. 

The ratio of 4.7 to i corresponds fairly closely 
with the ratio of the tensile strength of the two 
metals. It has been seen that the tensile strength 
of the steel of the Schoen wheel is about 124,000 
lbs. In some tests of cast iron that have been made 
it was found that samples of gray iron made from 




TRACK APPARATUS FOR ASCERTAINING WHEEL AND RAIL PRESSURES. 



first-class wheel mixtures broke at from 16,000 lbs. 
to 17,000 lbs, while test specimens, carefully ground 
from the white chilled iron of a car wheel, broke 
under loads as high as 36,000 lbs. 

The lack of any data on the stresses to which 
wheels are subjected in service, other than that 
based on theoretical calculations, necessitated the 
carrying out of a series of investigations which 
would throw some light on the subject from a practi- 
cal standpoint. The object was to determine the 
lateral thrust to which the wheels under high capac- 
ity freight cars may be subjected when moving over 
curves at different speeds, and, if possible, to develop 
the law in accordance with which the thrust in- 
creases as the speed of the car is increased. 

As an investigation of this kind had never before 
been undertaken, it was necessary to design and 
build a special piece of apparatus. 

The device as a whole may be divided into two parts : 
the track apparatus and the recording instrument. 

The track apparatus consisted of a section of rail 
3 ft. long held in position in the track and free to 
move outward by an amount sufficient to exert a 
pressure on a hydraulic cylinder in proportion to 
the lateral thrust against it. 

The recording instrument was set on a small table 
placed about 7 ft. from the track and was connected 
with the cylinder of the track apparatus by a ^-in. 
brass pipe. It consisted of an ordinary pressure gauge, 
having a maximum registration of 200 lbs. per sq. in., 
a recording pressure gauge and a pressure pump by 
which an initial pressure could be put on the whole 
system of piping. The ordinary pressure gauge was 



"3 



9./4- M/LES P£/f HOUfl 



/3.26 M/LES P£R HOUft 



/4:2JM/L£3 P£R HOUR 



2/.8/ M/LE6 PER HOUR 



30. 6/ M/LES PER HOUR 
SAMPLES OF SPEED REGISTRATIONS. 

one made by the Utica Steam Gauge Co. and was 
fitted with a diaphragm spring. It was carefully test- 
ed and the dial calibrated before being put in service. 

The recording pressure gauge was a modification 
of the Metropolitan recording gauge made by 
Schaeffer & Budenberg. The clockwork in it was 
removed and the paper drum driven by hand, so 
that a record of indefinite length could be obtained. 
The fact that this paper was driven by hand ex- 
plains the irregularity of the intervals elapsing be- 
tween the passage of the several wheels of the cars. 
This gauge also had a maximum registration of 200 
lbs. per sq. in. with a pen travel of 4 ins., the width 
of the paper. A Bourdon tube was used as the 
spring for this gauge. It was calibrated for each 
set of tests by the Utica gauge and its indications 
marked on the paper on which the record was taken. 

The piping and all spaces filled with liquid were 
so arranged that air pockets were entirely eliminated 



114 



and before work was commenced it was definitely 
ascertained that the whole space was completely 
filled with liquid free from bubbles of air. 

The speed of the experimental car as it passed 
the instrument was registered by means of two 
trips placed alongside the track and arranged to be 
struck by one of the journal boxes of the car as it 
passed. The trips closed an electric circuit passing 
through one of the coils of a double registering 
Morse telegraph instrument. When the trip was 
struck by the journal box, the circuit was tem- 
porarily broken and the pen lifted, leaving an open- 
ing in the line drawn on the strip of paper traveling 
through the instrument. The time was indicated 
by a clock making and breaking an electric circuit 
at half-second intervals. This circuit passed through 
the other coil of the register. The two records were 
made side by side and the intervals between the 
breaks, on the otherwise continuous line, showed the 
time elapsing between the striking of the two trips. 
These trips were spaced 66 ft. apart, so that the speed 
of the passing car could be readily calculated. Speci- 
mens of these records are shown in the accompanying 
diagram where the car was moving at 9.14, 13-26^ 
14.21, 21.81, and 30.61 miles per hour, respectively. 

Through the courtesy of the Pittsburgh, Cincin- 
nati, Chicago & St. Louis Ry., facilities were sup- 
plied for making this investigation of wheel stresses. 
The instrument was placed in the outer rail near the 
end of a curve of 1,307 ft. radius or about 4° 25'. 
The elevation of the outer rail was 3I ins., which is 
correct for a speed of 36.66 miles per hour. At the 
point where the records were taken the car was well in 



"S 







/J.,e6 /W/L £S /°£/9 HOUR 




TEST /V? 23. ^OQ. e. /907 
/7.>^& A7/LES /=£R /fOOR 



EXAMPLES OF LATERAL THRUST DIAGRAMS OF LOADED COAL CAR. 
TOTAL WEIGHT, 142,300 LBS., OR 4° 25' CURVE. 




Sf^EEO 9.35 MILES PER HOUR 




SPEED /^.03M/L£3 PER HOUR 

EXAMPLES OF LATERAL THRUST REGISTRATIONS OF LOADED COAL TRAINS, 
WITH CARS OF 100,000 LBS. CAPACITY. 

on the curve, with the trucks set in the normal posi- 
tion, and all the elements of enterino- the curve were 
removed. It may be added that the curve was a 
simple one, with no easement at either end. 

On the approach of a train, or the experimental 
car, an initial pressure was put on the piping 
system, in order that the movement of the register- 
ing pen might be reduced to a minimum and with 
it the effect of the inertia of the parts. This initial 



xi6 



pressure was varied according to the speed. In opera- 
tion the actual movement of the floating rail was 
imperceptible. The levers divided the actual move- 
ment by five at the diaphragm, which yielded only 
enough to take the expansion of the Bourdon tube 
and the diaphragm of the pressure gauge, when 
delivering from a cylinder 6 in. in diameter. 

Records were taken of a number of passing trains, 
and also a special series of measurements was made 
with a loaded coal car run at different speeds over 
the apparatus. Some of the records are shown in 
the accompanying diagrams. 

In the records of the loaded coal trains, taken as 
they passed, no memorandum of the weights of the 
cars was obtained. The weights were, however, 
approximately the same, and yet there were wide 
variations in the lateral thrusts of the wheel against 
the rail. For example: In the train moving at 
9.35 miles per hour these thrusts varied from 2,260 
lbs. to 7,210 lbs., with an average of 4,835 lbs. On 
another train, moving at 12.05 miles per hour, the 
thrust varied from 7,070 lbs. to 10,605 1^^-' with an 
average of 8,205 lbs.; while on another, moving at 
4.04 miles per hour, the average was 5,543 lbs., with 
a range from 4,450 to 6,635 ^^^- ^^ ^^^ ^^^^ ^ car reg- 
istered a thrust of 16,175 lbs. when moving at 14.35 
miles per hour. This wide variation in the lateral 
thrust of different cars in the same train at the instant 
of passing the apparatus was still more strikingly 
shown in the series of tests made with a single car. 

The tests with a single car consisted of ^^ runs over 
the apparatus, at speeds varying from 4.57 to 31.25 
miles per hour. The car used was a hopper-bottom 



117 



coal car of 100,000 lbs. capacity and weighing, 
when empty, 39,500 lbs. It was designated as of 
the Gl class of the Pennsylvania Lines West. The 
total weight of the loaded car was 142,300 lbs. 

This car, after being started some distance from 
the apparatus, was cut loose from the engine and 
allowed to drift over the track instrument. 

The following table gives the records that were 
made: 



Test 


Speed. 


Wheel 


Lateral Thrust. 


No. 


M.p. H. 


No. 


Lbs. 


I 


4-57 


r 


2,470 


" 


" 


2 


1,415 


'< 


" 


3 


1,69s 


« 


a 


4 


1.415 


2 
« 


7;63 


I 

2 


1.695 


« 


I( 


3 


1,415 


" 


(( 


4 




3 


10.43 


I 


2,545 


« 


" 


2 


1,770 


(i 


(1 


3 


1,695 


a 


" 


4 


1,695 


4 


7-39 


I 


2,400 


« 


(( 


2 


1,415 


« 


" 


3 


1. 41 5 


<( 


(1 


4 


1,415 


5 


8.57 


I 


2,120 


" 


a 


2 


1,270 


11 


u 


3 


1,415 


(< 


(( 


4 


1,415 


6 


8.20 


I 


1,840 


" 


" 


2 


1,415 


a 


(( 


3 


1. 41 5 


u 




4 


1,415 



118 



Test 


Speed. 


Wheel 


Lateral Thrust. 


No. 


M. p. H. 


No. 


Lbs. 


7 


9.60 


I 


1,695 


" 


" 


2 


I.415 


<< 


it 


3 


1,270 


« 


" 


4 




8 


10.21 


I 


3.250 


<( 


« 


2 


3'"o 


i( 


» 


3 


4,240 


« 


(( 


4 


3.250 


9 


9.60 


I 


3.535 


« 


(( 


2 


3.535 


« 


" 


3 


4,240 


(1 


" 


4 


3.19s 


lO 


9.60 


I 


3. 535 


" 


" 


2 


3.250 


i< 


« 


3 


4,380 


" 


<( 


4 


3.250 


II 


15.62 


I 


3,110 


(1 


" 


2 


2,970 


« 


(< 


3 


2,970 


« 


(( 


4 


2,400 


12 


11.00 


I 


4.950 


i( 


a 


2 


4,240 


« 


« 


3 


3,960 


« 


'* 


4 


3.8 IS 


13 


16.55 


I 


4,525 





« 


2 


3.535 


(t 


(( 


3 


4,525 


« 


" 


4 


3,395 


14 


14.18 


I 


3.815 


<( 


« 


2 


3.535 


i( 


" 


3 


5.935 


i( 


(( 


4 


4,665 


IS 


12.63 


I 


3,393 


" 


" 


2 


3.250 


« 


" 


3 


4,857 


l< 




4 


3.250 



119 



Test 
No. 


Speed. 
M. p. H. 


Wheel 
No. 


Lateral Thrust. 
Lbs. 


i6 

11 


I3;33 


I 

2 


4,810 
4,810 




II 


3 
4 


7.350 
5,800 


TEST OF AUGUST 6TH, 1907. | 


17 
(1 


9.14 
i< 

II 


I 

2 
3 

4 


6,645 

5,655 
4,950 
4,240 


18 


13.26 

II 
II 
<i 


I 
2 
3 
4 


8,055 
7,775 
7,635 
6,645 


19 
<i 


13.66 

II 
i< 


I 
2 
3 


10,460 
7,490 


(( 


II 


4 




20 
<< 


13-27 

11 

i< 


I 
2 
3 
4 


7,210 
6,645 
6,500 


21 


16.21 

II 


I 
2 


4,665 


" 


i< 


3 


6,220 


« 


li 


4 




22 
(1 


18.00 
<( 


I 
2 
3 


7,210 
6,645 


i< 


(1 


4 




23 


17.58 
II 


I 

2 
3 
4 


6,785 
6,360 

7,775 
6,645 


24 
II 

II 


14.21 

11 

II 


I 

2 

3 

4 


9,895 

9,470 

10,320 

8,480 



Test 
No. 


Speed. 
M.p. H. 


Wheel 
No. 


Lateral Thrust. 
Lbs. 


25 


10.91 


I 
2 


2,825 


« 




3 

4 


3."o 


26 

« 


18.46 

« 

« 


I 

2 
3 
4 


10,320 

9,190 

10,605 

10,320 


27 
<( 


21.81 


I 
2 


4,95° 






3 
4 


7.490 
5.230 


28 
It 


19.03 


I 

2 


16,785 


" 




3 

4 


7.350 
5,090 


29 
« 


25.10 
<( 


I 
2 

3 
4 


5.655 
5.655 
5.655 
3.675 


30 


25.10 
<( 


I 

2 
3 
4 


10.745 

9.330 

10,180 

9.615 


31 


27.91 

<( 
It 


I 
2 

3 

4 


10,605 
9.895 
9.615 


32 


31-25 


I 
2 


10,035 
8,200 


« 


(I 


3 

4 


11,025 

7,775 


33 


30.61 


I 
2 
3 
4 


12,445 

11,310 

12,865 

9,190 



/'^poo 




30 



S /O /S BO 2S 

S^£:£D /A/ A7//L£S- /'j^/? HOUfi 
DIAGRAM OF LATERAL THRUST OF LEADING WHEEL OF FORWARD TRUCK 
OF LOADED COAL CAR. TOTAL WEIGHT, 142,300 LBS., ON 4° 25' CURVE. 

The column headed "Wheel No." indicates the 
order in which the wheels passed over the apparatus. 
Thus: I indicates the front wheel of the forward 
truck; 2, the second wheel; 3, the front wheel of the 
rear truck, and 4 the rear wheel. The blank spaces 
in the column of lateral thrust indicate no record 
obtained, because of the fact that the initial pressure 
put on the apparatus was greater than the wheel 



3S 



thrust, so that the thrust produced no movement of 
the pen. Throughout the whole series of tests the 
weather was fine and the rail dry. 

For convenience of reference and comparison the 
lateral thrusts of the front wheel of the forward 
truck have been plotted on the accompanying dia- 
gram. This diagram shows graphically the wide 
variations in the lateral thrust of the wheel. From 
it it is impossible to deduce any positive ratio be- 
tween the speed and the thrust, but it shows that 
there is a relationship and that the higher the speed 
the greater the thrust. There are a number of 
records for the first wheel, extending from about 
7.63 miles an hour to 16.55 n^i^^s an hour that lie in 
a straight line drawn from just below the record of 
31.25 miles an hour of 10,035 ^^^- The line drawn 
through these points is represented by the equation: 

T = 333 V- 800 

in which 

V = Lateral thrust of wheel in lbs. 
T = Speed in miles per hour. 

This must be regarded as a tentative formula only 
and one which evidently will not hold for very low 
speed. But from the records that have been obtained 
it gives the lowest values and therefore it cannot be 
criticized as being too high. 

Attention is also called to the fact that the pres- 
sure seems to increase directly as the speed and not 
as the square of the speed which is the rate of in- 
crease of the centrifugal force. The probable rea- 
son for this is that none of the speeds recorded were 
equal to or exceeded the speed corresponding to 
the superelevation of the outside rail. Therefore, 



123 



centrifugal action has no effect. In running around 
a curve the car must be deflected from the tangent 
at a certain rate, and this requires a certain definite 
amount of power. If, then, this power is exerted in 
a short period of time, a higher pressure will be put 
against the rail than if the time was longer, and, 
therefore, the pressure will vary inversely as the 
time. So that if the car passes around the curve in 
half a minute the pressure will be twice what it 
would be if a minute was required. Hence the 
pressure at thirty miles an hour would be twice 
that at fifteen miles an hour. 

When the speed exceeds that for which the super- 
elevation is calculated centrifugal action will then 
begin to manifest itself, and there will then be a 
more rapid rise of pressure than would be found 
from the equation given on page 123. This additional 
increase would be in the ratio of the square of the 
speed. For example: At a speed of 36.66 miles 
per hour the centrifugal effect is balanced by the 
superelevation of the outer rail on the curve on 
which these investigations were made. At 40 miles 
per hour the centrifugal force is 1.19 times as great, 
and this 19 per cent, additional manifests itself as 
additional lateral thrust above that called for by the 
formula. 

Taking the car under consideration, weighing 
142,300 lbs., the centrifugal action would be 9,648 
lbs. at 36.66 miles per hour, 11,481 lbs. at 40 
miles per hour, and 14,568 lbs. at 45 miles per 
hour. The excess centrifugal force to be dis- 
tributed among the four wheels of the car at 
40 and 45 miles an hour would be, therefore. 



124 



1,833 ^^^- ^^^ 4>920 lbs. respectively. If 25 per 
cent, of this is taken by the front wheel, which 
is a low estimate of what would actually be im- 
posed, there would be an extra load of 458 lbs. and 
1,230 lbs. added to the stress given by the formula 
for that imposed on the front wheel. This then 
becomes 

11,408 lbs. at 36.66 miles per hour 
12,978 lbs. at 40 miles per hour 
15,415 lbs. at 45 miles per hour 

It must be remembered that these are minimum 
values, and that blows due to soft spots in the track, 
kinks in the curve, bent rails, low joints and cramped 
side bearings will greatly increase this thrust. Suffi- 
cient data, however, has not yet been obtained to 
warrant any estimate of how much this increase 
would be. The diagram shows that stresses far 
above those found from this tentative formula are 
imposed on the wheels. 

The extreme case occurred in test No. 19, where 
the thrust was 6,711 lbs. in excess of that found 
from the formula. If the blow or cramping which 
caused this excessive thrust at 13.66 miles per hour 
was to occur at a speed of 45 miles per hour, the 
thrust that might be expected would be 22,126 lbs., 
and if it were to be increased in proportion to the 
speed it would become more than 36,000 lbs. This 
may be an extreme and exceptional case, but the 
results obtained seem to indicate that at least as 
great a stress as this should be provided for. 

Referring again to the tests of flange strength made 
in 1905 by Professor Goss, in the 23 tests that were 



125 



made, the pressures required to break the flange 
ranged from 47,750 lbs. to 109,900 lbs., with an 
average of 75,874 lbs. This gives a possible factor 
of safety of a little more than 2.5 when the maximum 
stress is taken at 30,000 lbs., but it drops to a little 
more than 1.5 when the strength of the weakest 
wheel is taken as the basis of comparison. This is 
for new wheels. When they have become somewhat 
worn the strength of the flange is less and the factor 
of safety is decreased still more. If this loss of 
strength in the old wheel is taken at 10 per cent., 
because of metal worn away, the strength of the 
weakest wheel used in the tests referred to would be 
42,975 lbs., and this would allow a factor of safety 
above a maximum load of 30,000 lbs. of about 1.4. 

In this comparison it has been assumed that a car 
of 100,000 lbs. capacity will deliver the maximum 
thrust to the wheel on a 4I degree curve at 45 miles 
per hour. This assumption was made because the 
data was obtained from such a curve. It is evident 
that greater stresses would be imposed on curves of 
sharper radius. The outer thrust, where centrifugal 
action is eliminated, would probably vary inversely 
as the radius of curvature. There is no data, as yet, 
to support this position, but it appears probable. 
If on further investigation this relation is found to 
hold, then, instead of a thrust of 12,520 lbs. being 
put on the wheel, as in the case of a car moving over 
the 4° 25' curve at 40 miles an hour, there will be a 
thrust of nearly 22,800 lbs. when the same speed is 
maintained over a curve of 8°. To this must be 
added the extra stresses that may be set up by blows, 
cramping of the wheels between the rails, the binding 



iz6 



of side bearings and other causes which may result 
in an increase of the normal stress. 

But one weight of car and one arrangement of 
wheel base has been here considered. There is, as 
yet, no data to give any idea as to the effect of weight, 
its distribution on the wheels or the height of the 
center of gravity, all of which are undoubtedly 
important. 

On the other hand, in this discussion, the whole 
lateral thrust is considered as resisted by the flange. 
Under ordinary running conditions this is not the 
case, for the frictional resistance of the tread of the 
wheel on the rail must be subtracted from the total 
thrust. In the car under consideration the weight 
on the front wheel was 17,900 lbs. If the coefficient 
of friction is taken at 0.25 then 4,475 lbs. should be 
subtracted from the pressure given. This would 
reduce the maximum pressure, as it has been cal- 
culated for a speed of 45 miles per hour, to 31,525 
lbs. and the probable minimum to 10,930 lbs. It 
must be remembered, however, that the frictional 
resistance is apt to fail suddenly and that at all speeds, 
even where the frictional resistance of the tread on 
the rail is greater than the lateral thrust, there must 
be a pressure on the flange in order to effect the 
deflection of the car on the curve. 

In this comparison the front wheel of the leading 
truck only has been considered, because it is on this 
wheel that the heaviest lateral thrust is imposed. 
The table shows that, in general, the maximum 
lateral thrust is on the first wheel; the thrust on the 
second is less; on the third it falls between the first 
and the second, and on the fourth it is the lowest. 



127 



In considering the advisability of using cast iron 
wheels under high capacity cars, it should be borne 
in mind that the cast iron wheel averages approxi- 
mately one-half the life under the cars of 100,000 
lbs. capacity that it does under cars of 60,000 lbs. 
capacity. The use of the heavy braking pressure on 
long grades has been the cause of many failures, 
because of the additional strains set up due to the 
heating by the brake shoe. There is a consequent 
expansion of the rim, and the actual resisting 
strength of the flange is lowered below that shown 
in the laboratory tests, which were made with the 
wheel cold and the metal at its maximum strength. 
Roads having long, steep grades usually have 
numerous sharp curves also, and the wheels are 
likely to be subjected to the most severe stresses 
when they are least able to resist them. If the lateral 
thrust on the flanges of wheels, under a loaded car of 
100,000 lbs. capacity, runs up as high as 30,000 lbs., 
and the actual breaking strength of the flanges of 
cast iron wheels varies from 45,000 lbs. to 105,000 
lbs. under the most favorable conditions, the 
question seems pertinent, is it safe to use such 
wheels under high capacity cars, in view of the fact 
that cast iron wheels deteriorate rapidly with wear 
and successive brake-shoe heating? 

The answer depends upon what the user deems a 
proper factor of safety for such service or the 
risks he can afford to run. 



128 



PRESENTATION OF THE ADVAN- 
TAGES CLAIMED FOR THE 
SCHOEN SOLID FORGED AND 
ROLLED STEEL WHEEL AS 
BASED UPON THE RESULT OF THE 
INVESTIGATIONS SET FORTH IN THE 
FOREGOING CHAPTERS, TOGETHER 
WITH THE DEMONSTRATION OF 
SERVICE TESTS. 

BY THE SCHOEN STEEL WHEEL CO. 

The investigations of the physical and chemical 
properties of car wheels outlined in the preceding 
chapters show what is being done in the manufac- 
ture of car wheels and steel tires and the require- 
ments which must be met in service. Acting 
upon the accepted theory that steel must have a 
maximum amount of work put upon it to insure its 
integrity and efficiency, consideration of cast steel 
wheels has been ignored. It has been shown that 
the metal in the Schoen solid forged and rolled 
steel wheel is in all respects equal to if not better 
than the metal in standard brands of steel tires and 
wheels as regards physical properties. It would 
naturally be expected then that these wheels should 
compare favorably in wearing qualities and strength 
in actual service. This expectation has been com- 
pletely fulfilled by the wheels which have been running 
under tenders, freight and passenger cars, and street 
and interurban electric cars. The Schoen solid forged 
and rolled steel wheel has been found to give mater- 
ially greater mileage for the same limit of wear than 
steel-tired wheels under exactly the same conditions. 



129 




NS547 
roZ4L iV£:/^R ^77S M/LEAG£'P£/f^n^£/iR-2^6fa 



N?503 

rOT4L tV£/l/i .JSS M/L£/iQ£ ^£fi ^ H^E/tR- 322/7 



N5 522 
TOT/^L tV£4R .cJ42^ M/LEAGE RER^ tVEA/i- 33/43 

WEAR OF SCHOEN STEEL WHEELS UNDER POSTAL CARS, 
f 513 AND 547=154,733. 
t 503 AND 523 = 184,539. 



MILEAGE 



130 



As a fair example of what has been done with 
these wheels in heavy passenger car service the fol- 
lowing record is given of a test made on wheels 
placed under postal car No. 6545, running on the 
Pennsylvania Railroad between New York and St. 
Louis: The car weighed 154,000 lbs., carried on 
two six-wheel trucks, giving a weight per wheel of 
12,833 lbs. The wheels under this car ran 184,539 
miles with a wear ranging from .348 in. to .378 
in., or an average of .365 in. The mileage per 
iV in. of wear was 25,618. The tread was main- 
tained at all times in smooth condition and the 
wear on all of the wheels was remarkably uniform 
and even. 

Twelve pairs of wheels from the same lot were 
placed under one truck each of four postal cars on 
various runs. The average mileage of these wheels 
up to the time of first turning was 109,018, with a 
minimum of 87,375 miles and a maximum of 141,170 
miles. The pair of wheels giving this maximum 
mileage were worn .3185 in. and .2785 in. respectively. 
An average wear of .2597 in. in 109,018 miles was 
obtained from all 12 pairs, which is at the rate of 
419,703 miles per inch or 26,231 miles per Yt in- 
of wear. If the amount of metal removed by turning 
is added to the actual wear these figures are reduced 
to 234,202 miles per inch and 14,638 miles per yw 
in. of wear. The causes of removal of these wheels 
were 3 pairs for worn treads, 3 pairs for cut journals, 
I pair for a loose wheel, i pair for a thin flange and 
3 pairs for hollow and built-out flanges. At the 
time this record was taken the remaining pair of 
wheels had not been removed. 



131 



In electric traction work, where the service is 
much more severe than on steam roads, be- 
cause of the greater number of stops and the bad 
condition of the rails, and because of the fact that 
the majority of the wheels are motor driven, the 
mileage is less, but is still sufficiently high to show a 
decided advantage for the solid forged and rolled 
steel wheel over the cast iron wheel. The records of 
the Brooklyn Rapid Transit Co. show that from 
these wheels there was obtained a mileage per -^t in. 
of wear of 6,500 miles under electric freight cars 
running on the surface lines, and from 8,520 miles to 
9,750 miles under motor passenger cars. This is at 
the rate of about .0961 in. and .0641 in. respectively 
per 10,000 miles run, with the wheels still remaining 
in such good condition that turning was unnecessary. 
Still better results were obtained with these wheels 
under elevated motor cars of the same company. 
The records show wear at the rate of y^ in. per 
10,850 miles run, or a reduction of .0575 in. per 
10,000 miles. The flange and tread were still in 
good condition after having been worn down f in. 
and more. The accompanying tables and diagrams 
illustrate in a striking manner the remarkable service 
obtained by these wheels on this road and substan- 
tiate all of the claims made for them for electric 
railway work. 

From the data here presented it will be a simple 
matter to compare the value of the solid forged and 
rolled steel wheel with the value of the cast iron 
wheel in similar service. Dividing the life of the 
steel wheel by the life of the cast iron wheel gives 
the number of cast iron wheels required for an 



132 




WEAR OF SCHOEN STEEL WHEELS ON BROOKLYN RAPID TRANSIT R.R. 



133 



N5 9199 



N5 9204- 




WEAR OF SCHOEN STEEL WHEELS ON BROOKLYN RAPID TRANSIT R.R. 



134 



WEAR OF TREAD — SCHOEN ROLLED STEEL WHEELS. 









■J 




T3 




S) 


X.* 


.s 









g 


J3 


"S 


i 






ij 





(U 

J3 




1 


J3 


X. 


c 


<A 




H 


q1 


1 fe 


s . 


Type of Truck. 






B 


C 



c 


a 


i 


'o 


S 
Jo- 




1^ 




3 


OJ 








.0 

E 

3 


|a 





1 








^ 


s 


5 




iz; 


(2 


H 


w 








Lbs. 


In. 


In. 






In. 


In. 




Freight Truck . 


9358 


Flanged 


4,394 


31 


30% 


19,500 


None 


.1923 


3/8 


58,500 


" " 


9359 




4.394 


31 


30% 


19,500 


" 


•1923 


% 


58,500 


Motor Truck . . 


9199 




10,825 


33 


32 K 


58,500 


" 


.1282 


X 


204,100 


** " . . 


9204 




10,825 


33 


325i 


58,500 


" 


.1282 


K 


204,100 


" " . . 


91S8 




7,482 


33 


32j'8 


42,600 


" 


.1466 


^8 


85,400 


" " . . 


9190 




7,482 


33 


32% 


42,600 


" 


.1466 


^8 


85 ,400 


ElevatedRailway 






















Coach . . . 


ii773 


Flangeless 


4,262 


30 


29=540 


70,650 


" 


.115 


1%6 


10,811 


ElevatedRailway 






















Coach . . . 


21774 




4,262 


30 


i9^ 


70,650 




.1061 


M 


10,811 



equivalent mileage. The cost of renewals of the 
cast iron wheels must be added to the first cost 
and credit allowed for the scrap value of the old 
wheels removed. 

There are other items of cost, however, which, 
although difficult to accurately estimate are, never- 
theless, important. It must be remembered that 
each car has an earning capacity which is lost when- 
ever the car is in the shop for renewals or repairs, 
and this should be credited to the steel wheel which 
involves no such loss. Again, if the number of shop- 
pings for wheel defects can be materially reduced 
the same volume of traffic can be handled with fewer 
cars, thus saving investment in rolling stock and, 
what is almost as important in large cities, saving in 
expensive storage space. These advantages, tangible 
and intangible, have been so thoroughly demonstrated 
to street railway officers by the experience of a few 



135 




33-IN. STREET-CAR WHEEL. 



H'—, 




34-IN. STREET-CAR WHEEL. 



roads which early began to use solid steel wheels, 
that there is a large and growing demand for 
them in every class of electric service. For inter- 
urban roads especially, where the speeds are 
frequently as high as those obtained on steam 
railroads, solid steel wheels have been generally 
adopted for reasons of safety. The solid steel 



136 




33-IN. WHEEL FOR THE UNITED ELECTRIC RAILWAYS AND ELECTRIC 
CO. OF BALTIMORE, MD. 




34-IN. WHEEL FOR CITY AND INTERURBAN SERVICE, DESIGNED FOR SANDERSON & 
PORTER, CONTRACTORS AND ENGINEERS. 

wheel offers all of the advantages of wear claimed 
for the steel-tired wheel at a much smaller cost, 
and in addition greater safety, because of the im- 
possibility of parts coming loose. When compared 
with steel-tired or built-up wheels, in which the 
parts are shrunken on or bolted in place, and 
therefore liable to become slipped under the com- 
bined effect of expansion due to brake-shoe heat- 
ing and the torque of the motor, the advantages 
of a solid steel wheel for traction purposes become 
immediately apparent. 



137 



SJ'^M. 




33-IN. STREET-CAR WHEEL FOR NEW YORK CITY RAILWAY CO. 




34-lN. STREET-CAR WHEEL FOR PENNSYLVANIA AND MAHONING VALLEY 
TRACTION CO. 



The solid forged and rolled steel wheel was origi- 
nally developed to meet the severe requirements of 
service under high capacity freight cars and it is in 
this field that it has the widest possibilities of appli- 
cation. That there is a demand for these wheels is 
shown by the fact that more than 150,000 are now 
in use, 55,000 of them in service under 100,000 lbs. 
capacity cars, and the number is steadily increasing. 

It is difficult to make an estimate of the mileage 
cost of freight car wheels because of the incomplete 
records usually kept. From the best statistics avail- 
able, however, it appears that the mileage obtained 
from cast iron wheels under 100,000 lbs. capacity 
cars is between 25,000 miles and 30,000 miles. 



138 




3;3-lN. STEEL WHEEL. 



■J4^0M. 




-J' H 

34-IN. SUBWAY MOTOR-TRUCK WHEEL FOR THE INTERBOROUGH RAPID 
TRANSIT CO., NEW YORK. 



From the tests made of Schoen solid forged and rolled 
steel wheels under postal cars on the Pennsylvania 
Railroad it was found that there was obtained an 
average mileage of 14,638 per yV in., including wear 
and turning. Under heavy tenders, the mileage 
averaged 7,000 per ^ in. of wear and turning. The 
average of these two figures, 10,800 miles per yb^ in. 
of wear and turning, may be taken as the probable 
average service which can be obtained from these 
wheels under high capacity freight cars. The 
wheels furnished to the Pennsylvania Railroad for 
freight cars have a rim 2 in. thick with limit groove 
for wear cut | in. in from the inner edge. This gives 



139 




34-IN. STREET-CAR WHEEL FOR CHICAGO CITY RAILWAY CO. 




34-IN. STREET-CAR WHEEL FOR CONSOLIDATED RAILWAY CO., 
NEW HAVEN, CONN. 

a wearing thickness of if ins. available for service. 

At 10,800 miles per ^t i^i- of wear, the total mileage 

which can be obtained from these wheels is 20 x 

10,800=216,000 miles as against 30,000 miles for cast 

iron wheels, or a little more than seven times the life. 

If the first cost of a cast iron wheel is taken at ^10 

and its scrap value at ;^5, then the cost of cast iron 

wheels to give a life equivalent to the life of one 

Schoen solid forged and rolled steel wheel would be : 

7 cast iron wheels at ^10 each ^^70 

7 scrap wheels (credit) at ;^5 each ^35 



Actual cost of cast iron wheels 



fe5 



140 




AXLE AND WHEEL DESIGN SUBMITTED BY THE SCHOEN STEEL WHEEL CO. 

AS REQUESTED BY THE CENTRAL ELECTRIC RAILWAY COMMITTEE ON 

STANDARDIZATION FROM THEIR REPORT DATED MAY 23, 1907. 




AXLE AND WHEEL DESIGN SUBMITTED BY THE SCHOEN STEEL WHEEL CO. 

AS REQUESTED BY THE CENTRAL ELECTRIC RAILWAY COMMITTEE ON 

STANDARDIZATION FROM THEIR REPORT DATED MAY 23, 1907. 



141 



^'^~rfM- 




AXLE AND WHEEL DESIGN SUBMITTED BY THE SCHOEN STEEL WHEEL CO. 

AS REQUESTED BY THE CENTRAL ELECTRIC RAILWAY COMMITTEE ON 

STANDARDIZATION FROM THEIR REPORT DATED MAY 23, 1807. 




AXLE AND WHEEL DESIGN SUBMITTED BY THE SCHOEN STEEL WHEEL CO. 

AS REQUESTED BY THE CENTRAL ELECTRIC RAILWAY COMMITTEE ON 

STANDARDIZATION, FROM THEIR REPORT DATED MAY 23, 1907. 



142 



The original cost of the solid forged and rolled 
steel wheel may be taken at ^20 and its scrap value 
at the end of its life at ^5. Its total cost, therefore, 
would be ^^15 as against ^^35 for the equivalent num- 
ber of cast iron wheels required to give the same 
mileage. It is assumed that the cost of turning the 
solid steel wheel the required number of times during 
its life would equal the cost of removing and re- 
placing the cast iron wheels on the axle. 

The accompanying diagram shows graphically 
the comparative mileage, cost and strength of 
the ordinary cast iron wheel and the Schoen 

MILEAGE OF CAST IRON WHCEt 

lyilt-EAGC OF SCHOEN FOHGEO AWP ROLtED STEEL WHEEL 

COST PER 1000 MILES OF CAST IRON WHEELS DURING LIFE OF ONE SCHOEN STEEL WHEEL 
COST PER 100 MILES OF ONE SCHOEN STEEL WHEEL 

SAFervOF CAST iron wheel based upon its ELASTIC LIMIT 
SAFETY OF SCHOEN STEEL WHEEL BASED UPON ITS ELASTIC LIMIT 

CHART OF COMPARATIVE VALUES OF THE SCHOEN FORGED AND ROLLED 

STEEL Vi^HEEL, AND THE CAST IRON WHEEL FOR LARGE CAPACITY 

FREIGHT CARS AND COACHES. 

solid forged and rolled steel wheel. The first 
two lines show the comparative mileage, the next 
two show the comparative cost per 1,000 miles 
run, and the last two lines show the comparative 
safety of the two wheels based on the elastic 
limits of the metal of which they are made. The 
mileage is as 7 to i in favor of the steel wheel and the 
cost per 1,000 miles is as 2 to i in its favor. The 
elastic limit of cast iron as shown on the chart is 



143 



that given by Unwin: 10,500 lbs, in tension and 
21,500 lbs. in compression with a mean of 16,000 lbs. 
The elastic limit of the steel wheel is taken at 107,457 
lbs., a ratio of 6.7 to i in favor of the steel wheel. 
If the actual breaking strength of the flanges had been 
used in proportioning the relative lengths of these 
lines their ratio would have been as 8.6 to i in favor 
of the steel wheel as against the old M. C. B. stand- 
ard cast iron wheel and 5.3 to i in favor of the steel 
wheel as against the new reinforced flange cast iron 
wheel. It is evident, therefore, that the ratio of 6.7 
to I, as given on the chart, is conservative. 

Cast iron wheels under high capacity cars are a 
known source of danger, and on most mountain roads 
a careful inspection of every wheel is made when a 
freight train stops at the foot of a long grade. This 
costs time and money, and even then the inspec- 
tion is not always successful in detecting incipient 
failures which develop later with disastrous results. 
The loss of earning capacity of cars standing idle 
awaiting shopping for wheel defects is important 
in times of congestion of traffic. It is a fact that 
many roads are prevented from realizing the full 
benefit of large overload carrying capacity simply be- 
cause the cast iron wheels are not considered safe 
to carry such loads. 

In the foregoing pages many and important ad- 
vantages of the Schoen solid forged and rolled steel 
wheel have been demonstrated. Careful examina- 
tions of the metal of which the wheel is made have 
shown it to possess better physical properties than 
the best steel tires and wheels on the market. Ex- 
perience in service, with wheels under freight and 



144 



passenger cars, locomotive tenders and electric 
cars, proves that the wearing quality is superior 
to the best of its competitors. The investigation 
of the lateral thrust of the wheel against the 
rail gives conclusive evidence that the cast iron 
wheel, even when made of the best material and 
with the flange reinforced as in the latest designs, is 
not safe under high capacity cars at any but the 
lowest speeds. Finally, it has been shown that the 
solid forged and rolled steel wheel can be applied 
under freight cars in place of cast iron w^heels with 
an actual saving of $J per 100,000 miles run, or ^56 
per 100,000 car miles. In considering the question 
of car wheels for any service, therefore, from the 
standpoint of safety, mileage or cost, the solid forged 
and rolled steel wheel stands in front of all others. 



145 




The Schoen Steel Wheel 
Company's works at 
McKees Rocks, Pa. 



147 




Hydraulic presses, each with 
a capacity of eighteen million 
pounds, are used to forge 
the Schoen Solid Steel 
Car Wheel. 



149 




The most ingenious 
mechanism is required to 
roll and finish a Schoen 
Solid Steel Car Wheel. 



151 




One of the electric 
manipulators used for 
handling the steel blooms in 
the manufacture of Schoen 
Solid Steel Car Wheels. 



153 




Various types of hydraulic 
presses are used in forging 
Schoen Solid Steel 
Car Wheels. 



155 




Twelve hundred horse- 
power engines are coupled to 
each rolling mill used in the 
manufacture of Schoen 
Solid Steel Car Wheels. 



157 




These hydraulic presses were 
all especially designed to 
forge Schoen Solid Steel 
Car Wheels. 



159 




View in one of the power 
houses of The Schoen Steel 
Wheel Company's plant 
at McKees Rocks, Pa. 



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